Process for producing ethylene-vinyl alcohol copolymer resin, process for producing pellets and resin pellets

ABSTRACT

A process for producing an ethylene-vinyl alcohol copolymer resin, including feeding EVOH into an extruder, keeping the temperature of the melting resin in the extruder at 70 to 170° C., adjusting the amount of water in the extruder so that the water content right after being discharged from the extruder is 5 to 40 weight %, and extruding out the EVOH resin. The extruded EVOH resin is cut into EVOH pellets. Thereby, it is possible to obtain resin pellets in which no spherocrystals are observed in the center of the cross section of the resin when the cross section is observed by the use of a polarization microscope, or no lubricant is contained in the resin pellets, and the angle of repose is 23° or less when the resin pellets are laminated. Thus, it is possible to provide an ethylene-vinyl alcohol copolymer (EVOH) resin pellet having a reduced discharging load to the environment and capable of being fed into an extruder smoothly without being blocked, extruding stability, and thermal stability (long-run property).

FIELD OF THE INVENTION

The present invention relates to a process for producing anethylene-vinyl alcohol copolymer (hereinafter, also referred to as“EVOH”) with good thermal stability and a low production cost, a processfor producing resin pellets, and resin pellets obtained by the process.

BACKGROUND OF THE INVENTION

EVOH is widely used for food packaging, because it has a high gasbarrier property and excellent resistance properties against oil andorganic solvents, aroma retention property, transparency, and the like.For food packaging, various kinds of molding processes are employed.Examples of such molding processes includes an extrusion molding processfor films, a blow molding process for bottles, a vacuum molding processfor various kinds of packages, and the like. Such molding processesstart by feeding resin pellets into a hopper, etc. of an extruder.

However, there is a problem that conventional EVOH resin pellets tend tobe blocked in the hopper when the resins are fed into the extruder, andthus the resins are not fed into the extruder smoothly.

Furthermore, since the melting temperature should be 200° C. or more atthe time of the molding process, unless the polymer is provided with animproved thermal property, the polymer is deteriorated at the time ofmelt molding. As a result, fish eye or hard spots are formed, thusdeteriorating the quality of the products. Therefore, it is necessary toprovide the polymer with an improved thermal stability.

Hitherto, in order to provide EVOH with such a property, a method ofadding a minor component such as an acid material and/or a metal salt,etc. is well known. For improving the long-run property and theappearance deterioration caused by the gel and hard spots, etc., forexample, JP 64-66262A discloses an EVOH of a composition that contains0.0005-0.05 weight % (based on metal) of a metal salt belonging to groupII of the periodic table, 0.002-0.2 weight % of acid having a pKa of 3.5or more and a boiling point of 180° C. or more, and 0.01-0.2 weight % ofacid having a pKa of 3.5 or more and a boiling point of 120° C. or lessand which exhibits a certain flowability.

The following are examples of a well-known method for obtaining EVOHpellets to which the minor component is added as mentioned above.

(1) A method of spraying an aqueous solution of the minor component toEVOH pellets, blending thereof with a Henschel mixer, and then dryingthereof (JP 55-12108A).

(2) A method of mixing a minor component in the form of a powder to EVOHpellets, and dry-blending thereof with a super mixer (JP57-34148A).

(3) A method of immersing EVOH pellets in an aqueous solution containinga minor component and removing water from EVOH pellets, followed bydrying (JP64-66262A).

(4) A method of adjusting the water content of EVOH pellets to 20 to 80weight %, and bringing the EVOH pellets into contact with an aqueoussolution of at least one compound selected from the group consisting ofa boron compound, acetate and a phosphoric acid compound (WO/99/05213A).

However, in the method explained in the above (1) or (2), the minorcomponents cannot be contained in EVOH pellets sufficientlyhomogeneously, and it is difficult to control the added amount of theminor component. Thus, it is difficult to obtain products with a stablequality. Furthermore, the method explained in the above (3) or (4) isadvantageous in that it is easy to control the amount of the minorcomponent contained in the EVOH pellets by adjusting the concentrationof the solution. However, when the EVOH pellets treated by these methodsare molded by melt extrusion, the motor torque and torque variation ofthe extruder are increased. Therefore, in general, it is necessary toadd a lubricant to EVOH resin composition at the time of extrusion.However, the EVOH resin composition is used preferably for theapplications of food packaging, etc., and therefore, the use of suchlubricants is not necessarily preferable from the sanitary viewpoint.Thus, it has been demanded that the lubricants be reduced or avoided.

The EVOH pellets treated by the method (3) or (4) are generally obtainedas follows. A methanol solution of saponified EVOH is allowed toprecipitate in the form of a strand in a coagulation bath of awater/methanol mixed solution. The obtained strand is cut into pellets.However, in the case of EVOH of an ethylene content of less than 20 mol% and/or EVOH having a saponification degree of less than 95 mol %,strands are not precipitated easily in the coagulation bath, andfurthermore, cutting errors or contamination of fine powders easilyoccur, thus making it difficult to produce pellets stably. Occasionally,strands may not be precipitated, and paste-like EVOH is precipitated asa crumb-like product coagulated in an indeterminate shape. However, itis difficult to mix the minor component homogeneously into thecrumb-like precipitates processed by the methods (3) or (4). Thus, it isnot possible to obtain products of a stable quality.

On the other hand, even if EVOH of an ethylene content of 20 mol % ormore and/or the saponification degree of 95 mol % or more is used, whenthe strands are precipitated at high speed in order to improve theproductivity, strands are not precipitated stably. Thus, it is difficultto produce pellets stably. Consequently, it was not possible to obtainproducts of a stable quality by the method (3) or (4).

Furthermore, from the viewpoint of the production process, in theconventional method in which the EVOH pellets are immersed in a treatingsolution containing an acid material and/or a metal salt, a treatingbath or a treating tower for the immersion treatment is required. Thetreating solution used in such a treating bath or treating tower isrequired to be thrown away after use or recycled in order to add anappropriate amount of acid materials and/or metal salts again, after thetreatment of EVOH, because the acid materials and/or metal salts areconsumed after the treatment.

It is not preferable to throw away the treating solution in view of theinfluence on environment. Therefore, in general, the treating solutionis disposed of by way of a wastewater treating plant. Furthermore, whenthe treating solution is collected and reused, in order to obtainproducts having a stable quality, apparatus for adding acid materialsand/or metal salts again and apparatus for removing impurities such asoligomer, etc. in the treating solution are required.

As mentioned above, the conventional methods suffer from a problem thatlarge-scale treatment apparatus and a long treatment time are required,and that the production cost is high.

Furthermore, an example of a wet extrusion includes a melt extrusionmolding performed at certain energy (JP11-58500A), and melt extrusionmolding by controlling the temperature of cylinder to a certaintemperature (JP 11-58501A).

However, the above-mentioned conventional methods require complexoperations. Therefore, the methods are not preferable as a treatingprocess for producing pellets of EVOH resin.

Furthermore, when pellets of EVOH resin are fed to an extruder, meltedand then subjected to a molding process, if residue of a saponificationcatalyst contained in the resin at the time of production remains in thepolymer, the thermal stability may be deteriorated.

Hitherto, in order to remove the residue of the saponification catalystfrom the polymer, resin pellets are placed in a washing container andbrought into contact in the solid state with a washing water (water) soas to diffuse and extract residue from the inside of the resin pelletsto the outside (JP55-19242B).

However, the above-mentioned conventional method requires a long timeand a large washing apparatus and space.

Furthermore, in the above-mentioned conventional method, a large amountof water is attached to the resin. Therefore, in order to eliminate thewater, a hot-air drying using a dryer is required. In this case, thereis a problem that pellets occasionally are melted and attached to eachother depending upon the drying temperatures.

Furthermore, the conventional EVOH resin pellets are generally producedby a strand cutting method. That is, a strand (continuous stick-likeproduct) is obtained by extruding a solution of resin from a metal moldinto a poor solvent so as to precipitate, or a strand is obtained byextruding resins which are heated and melted and by cooling andsolidifying thereof. Then, the obtained strand is cut into pelletshaving the constant size by using a strand cutter (JP 3-61507A).However, since the strand cutting method requires a process forcontinuously precipitating or cooling and solidifying the extrudedresin, it is difficult to cut a large amount of resin with high accuracyin a short time. Therefore, there is a problem that strands cut offeasily. In particular, EVOH of a low ethylene content or EVOH of a lowsaponification degree suffers from the above-mentioned problemsignificantly, because the precipitating rate for allowing the strand tobe precipitated from the solution is slow.

Furthermore, when feeding water-containing EVOH resin pellets into theextruder, if a large amount of water is attached to the surface of theresin pellets, some problems arise. For example, pellets form bridges inthe hopper; pellets are blocked in a feeder; water vapor is generated inthe extruder, so that pellets of EVOH resin are melted and attached toeach other; and the like. Specific problems include, bridges are formedin the hopper in the feeder, and thus raw materials are not fed to theextruder sufficiently. Another problem is that surface water separatedin the feeder is fed to the extruder to generate water vapor at thelower part of the hopper, so that the raw material pellets are meltedand attached to each other. As a result, the raw material resins are notfed to the extruder sufficiently. In particular, in this case of thewater-containing EVOH, melting point of EVOH is lowered, the pellets arelikely to be melted and attached to each other at the lower part of thehopper. Furthermore, insufficient feeding of the raw materials maychange the feeding amount into the extruder. Thus, there arise someproblems, for example, the adding amount of acid-metal salt becomesunstable, deteriorating the thermal stability. Therefore, theimprovement in methods for effectively feeding water-containing EVOHresin pellets into an extruder has been demanded.

SUMMARY OF THE INVENTION

It is a first object of the present invention to provide a process forproducing EVOH, which reduces a discharge load to the environment, canbe fed into an extruder smoothly without being blocked, and is excellentin extruding stability and thermal stability (long-run property), aprocess for producing resin pellets therefrom, and resin pelletsproduced by the above-mentioned process.

The second object of the present invention is to provide a process forproducing EVOH resin and a process for producing pellets thereof,wherein residue of the saponification catalyst contained at the time ofproduction of the EVOH resin can be removed effectively, and the resincan be washed in a small space.

The third object of the present invention is to provide a method forremoving water from a water-containing EVOH resin by using an extruder,and a process for producing EVOH resin, in which additives can be addedinto EVOH resin effectively.

The fourth object of the present invention is to provide a method forcutting a water-containing and molten state EVOH resin right after beingdischarged from the extruder, thereby effectively cutting a large amountof polymers in a short time with high accuracy.

In order to attain the above-mentioned objects, according to a firstproduction process of the present invention, a process includes feedingEVOH into an extruder, keeping the temperature of the melting resin inthe extruder at 70-170° C., and adjusting an amount of water so that thewater content of EVOH right after being discharged is 5-40 weight %.

According to a second production process of the present invention, atleast one additive selected from carboxylic acid, a boron compound, aphosphoric acid compound, an alkali metal salt, and an alkali earthmetal salt is added into the extruder. It is preferable that theadditives are added to EVOH in a water-containing state and moltenstate.

According to a third production process of the present invention, thewater supplied to the extruder is a washing water for washing the EVOHresin, the resin is washed by the washing water, the washing water isdischarged in a liquid state from at least one place downstream from awashing water supply portion, and residue of the saponification catalystcontained at the time of production of the resin is removed.

According to a fourth production process of the present invention, amethod for removing water removes water in the form of liquid water orvapor water from a water-containing EVOH resin from at least one portionof the extruder.

According to a fifth production process of the present invention, theEVOH resin is cut into pellets after being discharged from the extruderand dried until the water content becomes 1 weight % or less.

According to a first EVOH resin pellet of the present invention, nospherocrystals are observed in the center of the cross section of theresin pellet when the cross section is observed by a polarizationmicroscope (with a magnification of 600).

According to a second EVOH resin pellet of the present invention, anangle of repose is 23° or less when the resin pellets are piled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view to illustrate an outline of a process usingan extruder used in Examples 1 to 4 according to the present invention.

FIG. 2 is a cross-sectional view showing a method for measuring an angleof repose of the resin pellet obtained in Examples 1 to 4 according tothe present invention.

FIG. 3 is a schematic view to illustrate a washing method of Examples 5to 10 in one embodiment according to the present invention.

FIG. 4 is a schematic view to illustrate an outline of a process ofadding a minor component after washing of Examples 5 to 10 in oneembodiment according to the present invention.

FIG. 5 is a schematic view to illustrate a method of removing water inthe form of liquid water or water vapor of Examples 11 to 18 in oneembodiment according to the present invention.

FIG. 6 is a schematic view to illustrate an outline of a process ofadding a minor component after removing water in the form of liquidwater or water vapor of Examples 11 to 18 in one embodiment according tothe present invention.

FIG. 7 is a schematic view to illustrate an outline of a process usingan extruder used in Examples 19 to 21 according to the presentinvention.

FIG. 8 is a schematic cross-sectional view showing how to cut resin by ahot-cut method in Examples 19 to 21 according to the present invention.

FIG. 9 is a front view showing a die of FIG. 8.

FIG. 10 is a schematic view to illustrate an outline of a process usingan extruder used in Examples 22 to 23 according to the presentinvention.

FIG. 11 is a cross-sectional partially cut-away view showing ahopper-feeder used in Examples 22 and 23 according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention mentioned above, by performing a wetextrusion using an extruder, it is possible to provide pellets of EVOHresin, which reduces a discharge load to the environment, can be fedinto an extruder smoothly without being blocked, are in excellent inextruding stability and thermal stability (long-run property).Furthermore, it is possible to provide EVOH resin pellets in which thepolymer is prevented from being deteriorated.

According to the first production process of the present invention, itis preferable that an ethylene content of EVOH is 3-70 mol %.Furthermore, it is preferable that the saponification degree of EVOH is80-100 mol %. Furthermore, it is preferable that the water content ofEVOH to be fed to the extruder is 0.5-70 weight %. Furthermore, it ispreferable that water is supplied/removed to/from the extruder so thatthe water content of the resin right after being discharged from theextruder is preferably 5-40 weight %, and more preferably 15-30 weight%. Furthermore, the temperature of resin in the extruder is preferably70-170° C., and more preferably 90-140° C.

It is preferable in the second production process of the presentinvention that at least one additive selected from carboxylic acid, aboron compound, a phosphoric acid compound, an alkali metal salt and analkali earth metal salt is added into the extruder. Thus, an excellentthermal property can be attained. Furthermore, among the additives,carboxylic acid having pKa at 25° C. of 3.5 or more is preferable. Apreferable example of carboxylic acid is acetic acid or lactic acid.

It is preferable in the second production process of the presentinvention that additive is added into the water-containing and moltenEVOH. Furthermore, it is preferable that the additive is added in theform of an aqueous solution. It is preferable that the extruder has akneading portion. Furthermore, it is preferable that the additive isadded at the kneading portion of the extruder. Furthermore, it ispreferable that there are one or two adding portions.

It is preferable in the third production process of the presentinvention that the residue of the saponification catalyst contained inEVOH fed into the extruder is an alkali metal ion and that the contentof the ion is 0.1-5 weight % based on metal. Furthermore, the washingwater is an aqueous solution of acid having a pKa at 25° C. of 3.5 ormore is preferable. Furthermore, it is preferable that the washing wateris discharged by at least one means selected from a dewatering slit anda dewatering hole. Furthermore, after the washing water is discharged,preferably water is removed in the form of liquid water or vapor waterto adjust the water content of the resin so that the water content ofthe resin right after being discharged from the extruder is 5-40 weight%, additive is added into the extruder, and then the resin compositionis extruded from the extruder, followed by cutting. Furthermore, it ispreferable that the content of alkali metal ions contained in the washedEVOH resin is 0.05 weight % or less based on metal.

It is preferable in the fourth production process of the presentinvention that the method for removing water uses at least one meansselected from a dewatering slit and a dewatering hole. Furthermore, itis preferable that the water-containing EVOH is in a molten orsemi-molten state.

It is preferable in the fifth production process of the presentinvention that the resin is cut in a molten state. Furthermore, it ispreferable that a method of cutting the resin is at least one methodselected from a hot-cut method and an under-water cut method.Furthermore, after the copolymer is cut, preferably it is dried so as tohave a water content of 1 weight % or less.

It is preferable in the first to fifth production processes of thepresent invention that the method for feeding the pellet is a volumetricfeeding method in which the pellet is fed into the extruder continuouslyat a constant amount by using a volumetric feeder.

Hereinafter, the present invention will be described by way ofembodiments with reference to drawings. FIG. 1 is a schematic view toillustrate an outline of a process of a first embodiment according tothe present invention. A water-containing EVOH is fed from a rawmaterial feeding portion 1 of a twin screw extruder 20. EVOH, which isin a water-containing and a molten or semi-molten state, is fed forwardby a full-flight screw 2, and kneaded at an inverted flight screw 3. Ata vent cylinder 7, excess water is removed, and thus the water contentis adjusted. Thereafter, EVOH is fed forward by a full-flight screw 4. Apredetermined amount of additives are added into the extruder from aminor component adding portion 8. Then, EVOH is kneaded at an invertedflight screw 5, passes through a full-flight screw 6, is discharged froma discharge portion 11 and is pelletized downstream from the dischargeopening 11. Reference numeral 9 denotes a temperature sensor fordetecting and controlling temperature of EVOH, and 10 denotes a cylinderbarrel.

Next, FIGS. 3 and 4 are schematic views to illustrate a washing methodin the second embodiment according to the present invention. In FIG. 3,EVOH is fed from a raw material feeding portion 101 of a barrel 111 of atwin screw extruder 110. EVOH, which is in a water-containing and amolten or semi-molten state, is fed forward by a full-flight screw 105 aof a screw 112 and supplied with water, which is a washing water, from awashing water supply portion 102. Next, EVOH is kneaded at an invertedflight screw 106, and fed forward by a full-flight screw 105 b. Excesswater is squeezed and removed from EVOH at a dewatering portion 103. Atthe time of removing the excess water, the residue of the saponificationcatalyst generated during the production process is washed and removedfrom EVOH. Thereafter, EVOH passes through a seal ring portion 107 and afull-flight screw 105 c and then is discharged from a discharge portion(not shown). Reference numeral 104 denotes a temperature sensor fordetecting and controlling the temperature of EVOH.

FIG. 4 is a schematic view to illustrate an outline of a process foradding a minor component after washing in one embodiment according tothe present invention. EVOH is fed from a raw material feeding portion123 of a barrel 121 of a twin screw extruder 120. EVOH, which is in awater-containing and a molten or semi-molten state, is fed forward by afull-flight screw 128 a of a screw 122 and supplied with water, which isa washing water, from a washing water supply portion 124. Next, EVOH iskneaded at an inverted flight screw 129 a, and is fed forward by afull-flight screw 128 b. Excess water is squeezed out and removed fromEVOH at a dewatering portion 125 a. At the time of removing the excesswater, the residue of the saponification catalyst generated during theproduction process is washed and removed from EVOH. Thereafter, EVOHpasses through a seal ring portion 130 and a full-flight screw 128 c,and then is further subjected to dewatering or degassing treatment at adewatering portion 125 b. Next, additives are added from a minorcomponent adding portion 126, the resin is kneaded at an inverted flightscrew 129 b, passes through a full-flight screw 128 d and then isdischarged from a discharge portion (not shown). Reference numeral 127denotes a temperature sensor for detecting and controlling thetemperature of EVOH.

FIGS. 5 and 6 are schematic views to illustrate a degassing dewateringmethod of the third embodiment according to the present invention. Awater-containing EVOH is fed from a raw material feeding portion 201 ofa barrel 211 of a twin screw extruder 210. EVOH, which is in awater-containing and a molten or semi-molten state, is fed forward by afull-flight screw 204 a of a screw 212, and kneaded by an invertedflight screw 205. At a dewatering portion 202 including a dewateringslit and a dewatering hole, excess water is removed in the form ofliquid water or water vapor, and thus the water content is adjusted.Thereafter, EVOH is fed forward by a full-flight screw 204 b, andfurther fed to a discharge portion (not shown). Reference numeral 203denotes a temperature sensor for detecting and controlling thetemperature of EVOH.

FIG. 6 is a schematic view to illustrate an outline of a process ofadding an additive after excess water is removed in the form of liquidwater or water vapor in one embodiment according to the presentinvention. A water-containing EVOH is fed from a raw material feedingportion 223 of a barrel 221 of a twin screw extruder 220. EVOH, which isin a water-containing and a molten or semi-molten state, is fed forwardby a full-flight screw 227 a of a screw 222, and kneaded at an invertedflight screw 228 a. At a dewatering portion 224 including a dewateringslit and a dewatering hole, excess water is removed in the form ofliquid water or water vapor, and thus the water content is adjusted.Then, EVOH is fed forward by a full-flight screw 228 b, and further fedto a discharge portion (not shown). Reference numeral 226 denotes atemperature sensor for detecting and controlling the temperature ofEVOH.

FIGS. 7 to 9 are schematic views to illustrate an outline of a processin a fourth embodiment according to the present invention. In FIG. 7, awater-containing EVOH is fed from a raw material feeding portion 311 ofa twin screw extruder 310. EVOH, which is in a water-containing and amolten or semi-molten state, is fed forward, and kneaded at an invertedflight screw 312. The amount of water in EVOH is adjusted at adewatering slit 313. Then, EVOH is fed forward to a discharge portion321. The discharge portion 321 is equipped with a cutter 320 (which isillustrated in detail in FIGS. 8 and 9). A circulating water of thecutter is supplied from a cooling water supply portion 322, and thecooling water and the pellet are discharged from the pellet dischargeportion 323.

FIG. 8 is a schematic cross-sectional view showing a cutting process bya hot cut method. Water-containing EVOH discharged from a dischargeportion 331 of a twin-screw extruder is cut by the rotation of arotation blade 333 right after the EVOH is extruded from a die 322.Reference numeral 334 denotes a rotation axis directly connected to arotation blade 333. Cooling water 337 is supplied from a cooling watersupply port 336 to a cutter box 335 to form a water membrane 338therein. The water membrane 338 cools down the pellet right aftercutting. The cooling water and the pellet 340 are discharged from apellet discharge portion 339. FIG. 9 is a front view of a die 332. Thewater-containing EVOH is discharged from holes 341.

The cutting method in water (for example, an under-water cuttingapparatus) is similar to the hot-cut method. The difference between themis that in the in-water cutting apparatus, cooling water substantiallyfills the cutter box 341.

FIGS. 10 and 11 are schematic views to illustrate an outline of aprocess of the fifth embodiment according to the present invention. InFIG. 10, a water-containing EVOH is fed from a raw material feedingportion 401 of a twin screw extruder 420. EVOH, which is in awater-containing and a molten or semi-molten state, is fed forward by afull-flight screw 402, and kneaded at an inverted flight screw 403. At avent cylinder portion 407, excess water is removed from EVOH, and thusthe water content is adjusted. Thereafter, EVOH is fed forward by afull-flight screw 404, and a predetermined amount of additives is addedinto the extruder from a minor component adding portion 408. Then, EVOHis kneaded at an inverted flight screw 405, passes through a full-flightscrew 406, is discharged from a discharge portion 411, and is pelletizeddownstream from the discharge portion 411. Reference numeral 409 denotesa temperature sensor for detecting and controlling temperature of EVOHand 410 denotes a cylinder barrel.

FIG. 11 is a cross-sectional partially cut-away view showing ahopper-feeder used in the process in one embodiment according to thepresent invention. The hopper-feeder 430 includes a hopper 431containing resin pellets with a lid 432, a level switch 433 detectingthe amount of resin pellets, a stirrer 434 preventing resin pellets frombeing bridged, a motor 436 for rotating a screw 437, a duct 438 forfeeding resin into the extruder, and a base 435.

It is preferable that EVOH used in the present invention is one obtainedby saponifying ethylene-vinyl ester copolymer. The content of ethyleneis generally 3-70 mol %. From the viewpoint of providing molded articleshaving high gas-barrier property and excellent melt moldability, thecontent of ethylene is preferably 10-60 mol %, more preferably 20-55 mol%, and most preferably 25-55 mol %. Furthermore, the saponificationdegree of the vinyl ester component is 80 to 100 mol %. From theviewpoint of providing EVOH having a high gas barrier property, thesaponification degree is preferably 95 mol % or more, and morepreferably 99 mol % or more.

On the other hand, EVOH having an ethylene content of 3-20 mol % is usedsuitably for EVOH provided with water solubility. Such an aqueoussolution of EVOH has an excellent gas barrier property, a film formationproperty, and is used for an excellent coating material.

EVOH having a saponification degree of 80-95 mol % is used suitably forimproving the melting moldability. It may be possible to use such EVOHsingly. It also is suitable to use such EVOH by blending with EVOH ofsaponification degree of 99 mol % or more.

However, from the viewpoint of the production process, it is difficultto precipitate the above-mentioned EVOH of ethylene content of 3-20 mol% and EVOH of the saponification of 80-95 mol % by extruding a methanolsolution of EVOH into a coagulation bath in the form of a strand by aconventional process. Thus, it was difficult to produce pellets stably,and it was also difficult to allow acid materials and metal salts to becontained in the pellets. It was also difficult to extract residue ofsaponification catalyst from the pellets by diffusion. The presentinvention makes it possible to produce pellets stably, and to add anacid material and metal salt into the pellets. For this reason, thepresent invention has a great significance.

With an ethylene content of EVOH less than 3 mol %, the resulting EVOHis poor in melt moldability, and may be deteriorated in waterresistance, thermal resistance, and gas barrier property under highhumidity. On the other hand, with an ethylene content of EVOH more than70 mol %, the resulting EVOH does not provide a satisfactory gas barrierproperty, printability, or the like. Furthermore, with thesaponification degree less than 80 mol %, the resultant EVOH does notprovide satisfactory gas barrier property, coloring resistance, andhumidity resistance.

The following is an explanation of a process for producing EVOH.Polymerization of ethylene and vinyl ester is not limited to solutionpolymerization. For example, any of solution polymerization, suspensionpolymerization, emulsion polymerization, and bulk polymerization may beused. In addition, continuous polymerization and batch-typepolymerization may be employed. Hereinafter, as an example, conditionsfor batch-type solution polymerization are explained.

Solvent: Alcohol is preferable. However, other organic solvents capableof solving ethylene, vinyl ester and ethylene-vinyl ester copolymer(dimethylsulfoxide, etc.) can be used. Examples of useful alcoholsinclude methyl alcohol, ethyl alcohol, propyl alcohol, n-butylalcohol,t-butylalcohol, etc. Particularly, methyl alcohol is preferable.

Catalyst: Examples of useful catalysts include an azonitrile initiator,for example, 2,2-azobisisobutyronitrile,2,2-azobis-(2,4-dimethylvaleronitrile),2,2-azobis-(4-methoxy-2,4-dimethylvaleronitrile),2,2-azobis-(2-cyclopropyl propionitrile), and the like, and an organicperoxide initiator, for example, isobutyryl peroxide, cumylperoxyneodecanoate, diisopropyl peroxycarbonate, di-n-propylperoxydicarbonate, t-butyl peroxyneodecanoate, lauroyl peroxide, benzoylperoxide, t-butyl hydroperoxide, and the like.

Vinyl ester: Vinyl acetate, fatty acid vinyl ester (vinyl propionate,pivalic acid vinyl, etc.) may be used. Furthermore, EVOH may contain0.0002-0.02 mol % of vinylsilane compound as a copolymer component.Examples of vinylsilane compounds include, for example, vinyltrimethoxysilane, vinyl triethoxysilane, vinyltori(β-methoxy-ethoxy)silane, γ-methacryloxy propylmethoxysilane, and the like. Among them,vinyl trimethoxysilane and vinyl triethoxysilane are preferable.

(1) Temperature: 20-90° C., preferably 40-70° C.

(2) Time: 2-15 hours, preferably 3-11 hours.

(3) Polymerization rate: 10-90%, preferably 30-80% with respect to theprepared vinyl ester.

(4) Resin content in solution after polymerization: 5-85%, preferably20-70%.

(5) Ethylene content of copolymer: 3-70 mol %, preferably 10-60 mol %,more preferably 20-55 mol %, and most preferably 25-55 mol %.

Moreover, in addition to ethylene and vinyl ester, it is possible tocontain a small amount of monomer capable of being copolymerized withthe ethylene and vinyl ester. Examples of such monomers include, forexample, α-olefin such as propylene, isobutylene, α-octene, α-dodecene,etc.; unsaturated acid such as acrylic acid, methacrylic acid, crotonicacid, maleic acid, itaconic acid, etc., and anhydrate thereof, salt, ormono- or di-alkyl ester, etc.; nitrile such as acrylonitrile,methacrylonitrile, etc.; amide such as acrylamide, methacrylamide, etc.;olefin sulfonic acid such as ethylene sulfonic acid, allyl sulfonicacid, meta allyl sulfonic acid, etc. or salt thereof; alkyl vinyl ether,vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinylidene chloride,etc.; and the like.

After a predetermined conversion is obtained after a predetermined timeof polymerization, a polymerization inhibitor is added if necessary soas to evaporate and remove unreacted ethylene gas, and then unreactedvinyl ester is removed. The method for removing unreacted vinyl esterfrom ethylene-vinyl ester copolymer from which ethylene has beenevaporated and removed is, for example, a method in which thecopolymerization solution is supplied continuously at a constant ratefrom the upper part of a tower that is filled with a Raschig ring, vaporof organic solvent is blasted from the bottom part of the tower andmixed vapor of organic solvent such as methanol etc., and unreactedvinyl ester is distilled from the upper part of the tower.

An alkali catalyst is added into the copolymer solution from whichunreacted vinyl ester is removed so as to saponify the vinyl estercomponent of the copolymer. The saponification can be performed by anyof a continuous method and a batch type method. Examples of alkalicatalyst include sodium hydroxide, potassium hydroxide, alkali metalalcoholate, and the like. The following are the conditions of thebatch-type saponification.

(1) concentration of the copolymer solution: 10-50%

(2) reaction temperature: 30-65° C.

(3) amount of catalyst used: 0.02-1.0 equivalence (with respect to avinyl-ester component)

(4) time: 1-6 hours

The EVOH after reaction contains alkali catalyst, by-product salts,other impurities, and the like, and it is preferable that suchimpurities are removed if necessary by neutralization and washing.

The present invention provides a process for producing an ethylene-vinylalcohol copolymer resin, including feeding EVOH into an extruder,keeping the temperature of the melting resin in the extruder at 70-170°C., adjusting an amount of water by supplying/removing water into/fromthe extruder, and discharging the copolymer having a water content rightafter being discharged of 5-40 weight %. A shape of EVOH before feedinginto the extruder is not particularly limited. It is possible preferablyto use a pellet obtained by cutting strand precipitated in a coagulationbath, furthermore to use a crumb-like precipitate formed of coagulatedEVOH paste in an indeterminate form. Furthermore, EVOH paste can be feddirectly into the extruder.

The lower limit of the water content of EVOH before being fed into theextruder is preferably 0.5 weight % or more, more preferably 5 weight %or more, and particularly 7 weight % or more. Furthermore, the upperlimit of the water content of EVOH before being fed into the extruder ispreferably 70 weight % or less, more preferably 60 weight % or less, andparticularly 50 weight % or less. If the water content of EVOH beforefeeding into the extruder falls within the above-mentioned range, it ispossible to obtain a molten state EVOH at the temperature lower than themelting point of dry EVOH. Thus, it is possible to inhibit the thermaldeterioration of EVOH in the extruder and to attain a good extrudingstability.

When the water content is less than 0.5 weight %, the effect ofinhibiting the thermal deterioration of EVOH in the extruder may beinsufficient. On the other hand, when the water content is more than 70weight %, the phase separation between resin and water contained in theresin is likely to occur in the resin composition of EVOH. If such aphase separation occurs, the surface of the resin becomes wet, thusincreasing the friction. As a result, bridges may be formed in thehopper of the extruder, which may adversely affect the productivity ofpellets of resin composition of EVOH.

The method of adjusting the water content of EVOH before being fed intothe extruder is not particularly limited. In increasing the watercontent, a method of spraying water to resin, a method of immersingresin in water, a method of bringing resin into contact with watervapor, and the like, are employed. Furthermore, in reducing the watercontent, appropriate drying methods may be employed. A method of dryingresin by the use of, for example, a fluid type hot-air dryer or aventilation hot-air dryer may be employed. From the viewpoint ofreducing unevenness of drying, the fluid type hot-air dryer ispreferred. Furthermore, from the viewpoint of inhibiting the thermaldeterioration, the drying temperature is preferably in 120° C. or less.

The temperature of the resin in the extruder is preferably 70-170° C.When the temperature of resin is less than 70° C., EVOH may not bemelted completely. Furthermore, when at least one additive selected fromcarboxylic acid, a boron compound, a phosphoric acid compound, alkalimetal salt, and alkali earth metal salt is added, the effect ofimproving the diffusion property may be insufficient. The resintemperature is preferably 80° C. or more, and more preferably 90° C. ormore. Furthermore, when the resin temperature is more than 170° C., EVOHis susceptible to thermal deterioration. Furthermore, when at least oneadditive selected from carboxylic acid, a boron compound, a phosphoricacid compound, alkali metal salt, and alkali earth metal salt is addedin a form of aqueous solution, if the resin temperature is more than170° C., water evaporates radically. Consequently, it may be difficultto mix EVOH with the aqueous solution at the preferable concentration ofthe aqueous solution. The resin temperature is preferably 150° C. orless, more preferably 140° C. or less, and particularly 130° C. or less.The method of adjusting such resin temperatures is not particularlylimited, but a method of setting the temperature inside the cylinder inthe extruder at an appropriate temperature is preferable.

In the present invention, the resin temperature denotes a temperaturedetected by the temperature sensor provided at the cylinder of theextruder, and detected around the discharge portion at the tip of theextruder.

According to the present invention, it is possible to wash and removethe residue of the saponification catalyst contained at the time ofproducing the EVOH in the extruder. Specifically, the EVOH resin is fedinto the extruder, a washing water is supplied from at least one portionof the extruder, the resin is washed, and the washing water isdischarged from at least one place downstream from a washing watersupply portion. This method is preferable because washing is performedeffectively and a large washing space is not required as compared withthe conventional method in which resin pellets are placed in the washingcontainer and is brought into contact with the washing water in a solidstate to extract the residue of the saponification catalyst bydiffusion.

In this case, it is preferable that the residue of saponificationcatalyst contained in EVOH fed into the extruder is an alkali metal ion.

The content of the alkali metal ion contained in EVOH fed into theextruder is preferably 0.1-5 weight %, more preferably 0.2 weight % ormore, and particularly 0.5 weight % or more, based on metal.Furthermore, the content is more preferably 4 weight % or less, andparticularly 3 weight % or less. When the content is less than 0.1weight %, EVOH can be produced sufficiently by the conventional processin a small space, and so it is less significant to employ the process ofthe present invention. On the other hand, when the content is more than5 weight %, it is necessary to have an extruder of large L/D forsufficient washing, which may lead to cost increases.

Furthermore, in this case, it is preferable that the content of alkalimetal ions contained in EVOH after washing is preferably 0.05 weight %or less, more preferably 0.04 weight % or less, and particularly 0.0.3weight % or less, based on metal. The content of more than 0.05 weight %is not preferable because the thermal stability of EVOH is deteriorated.

Furthermore, the washing water used herein is not particularly limitedas long as it is capable of removing the residue of the saponificationcatalyst, however, an aqueous solution of acid having a pKa of 3.5 ormore at 25° C. is preferable. When an aqueous solution of acid havingpKa at 25° C. of less than 3.5 is used, EVOH may not provide asatisfactory coloring resistance or inter layer adhesiveness. Among suchacids, a carboxylic acid is preferable. In terms of cost effect, aceticacid is preferable. The concentration of the aqueous solution of aceticacid is preferably 0.01-10 g/liter, and more preferably 0.1-2 g/liter.

It is preferable that the supplied amount of washing water is 0.1-100liter per 1 kg of feeding resin.

The method of adding washing water is not particularly limited as longas it is capable of adding washing water into an extruder. An example ofan adding method includes a method of forcing the washing water by usinga plunger pump, etc., and the like. A discharge portion is notparticularly limited as long as it is positioned downstream from theadding portion and can discharge liquid from the extruder. A preferableexample is a dewatering slit or a dewatering hole. Moreover, a pluralityof adding portions or a plurality of discharge portions may be provided.

Furthermore, in the present invention, after the above-mentioned washingor without washing, it is preferable that water or water vapor isremoved from a water-containing EVOH in the extruder. Specifically, itis preferable that at least one selected from water liquid or watervapor is discharged from at least one place in the extruder. Thedischarging method is not particularly limited. An example includes amethod of discharging washing water from a dewatering slit, dewateringhole or a vent-port.

Among them, the dewatering slit or dewatering hole is preferable. Sincein the case of using these means, water can be discharged in the form ofliquid water or water vapor, it is possible to remove water efficientlyfrom resin of a high water content. From this viewpoint, the dewateringslit or dewatering hole is generally more effective than the vent-port,which can discharge only water vapor. Furthermore, when water isdischarged through the vent-port, resin tends to attach to thevent-port, and such attached resins are deteriorated and enter theextruder. Again, a dewatering slit or dewatering hole is preferable.

Moreover, as the vent-port, a vacuum vent for removing water vapor underreduced pressure or an open vent for removing water vapor under ambientpressure can be used.

Furthermore, when the dewatering hole is used, molten resin may leakfrom the hole. For this reason, the watering hole is preferred. Apreferable example of such a dewatering slit includes a wedge wiredewatering slit or a screen mesh type dewatering slit. Herein, the wedgewire denotes a wire having a wedge shape, that is, a triangular prismshape cross section. In the wedge wire dewatering slit, the wedge wiresare arranged with a predetermined gaps and water from the resin isextruded out through the gaps.

Moreover, the above-mentioned dewatering means may be used singly or aplurality of the same kinds of means may be used, or a combination ofdifferent kinds of means may be used. For example, it is possible toremove some amounts of water from resin of a high water content with adewatering slit and then further removing water by the vent-port locateddownstream from the dewatering slit.

The water content of the pellets of resin composition of EVOH rightafter being discharged from the extruder is preferably 5-40 weight %.When the water content right after being discharged from the dischargeportion is more than 40 weight %, the phase separation between a resinand water contained in the resin may occur in the resin composition ofEVOH. As a result, strands after being discharged from the extruder mayfoam easily. The water content is preferably 35 weight % or less, andmore preferably 30 weight % or less. Furthermore, when the water contentis less than 5 weight %, the effect of inhibiting the deterioration dueto heating of EVOH in the extruder may be insufficient. The resultantEVOH pellets may not be provided with a satisfactory coloringresistance. The water content is preferably 10 weight % or more, andmore preferably 15 weight % or more.

At least one additive selected from carboxylic acid, a boron compound, aphosphoric acid compound, alkali metal salt, and alkali earth metalsalt, can be added singly, but a plurality of the additives may be addedin the preferable ranges mentioned below, in accordance with embodiment.Thereby, it is possible to improve various kinds of performances of theEVOH resin composition pellet.

It is preferable that carboxylic acid is added to the EVOH resincomposition pellets of the present invention from the viewpoint ofimproving the thermal stability. In this case, carboxylic acid havingpKa of 3.5 at 25° C. is preferable. When an aqueous solution ofcarboxylic acid having pKa at 25° C. of less than 3.5 is used, it isdifficult to control the pH of the resin composition of EVOH.Furthermore, the resin composition of EVOH may not be provided with asatisfactory coloring resistance or interlayer adhesiveness. Examples ofcarboxylic acid include oxalic acid, succinic acid, benzoic acid, citricacid, acetic acid, lactic acid, and the like. In terms of cost effect,acetic acid or lactic acid is preferably used.

The content of carboxylic acid in the pellets of dried EVOH resincomposition is preferably 10-5000 ppm. When the content of carboxylicacid is less than 10 ppm, coloring may occur at the time of meltmolding. Furthermore, when the content of carboxylic acid is more than5000 ppm, sufficient interlayer adhesiveness may not be obtained. Thelower limit of the content of carboxylic acid is preferably 30 ppm ormore, and more preferably 50 ppm or more. The upper limit of carboxylicacid is preferably 1000 ppm or less, and more preferably 500 ppm orless.

It is also preferable that a phosphoric acid compound is added to theresin composition pellets of EVOH in terms of the improvement of thethermal stability. The content of phosphoric acid compound in thepellets of dried EVOH resin composition is preferably 1-1000 ppm. Byadding phosphoric acid compound within an appropriate range, it ispossible to inhibit the occurrence of color development and formation ofgel and hard spots. The improvement effect by the addition of phosphoricacid compound is significant at the time of the long-run formation usingpellets of EVOH resin compositions and at the time of collectingproducts. Examples of phosphoric acid compounds include various kinds ofacids such as phosphoric acid, phosphorous acid, or their salt, etc.thereof, however, the present invention is not necessarily limited tothese materials. For phosphoric acid salt, any forms of primaryphosphate, secondary phosphate, or tertiary phosphate may be employed.Also, the cationic species thereof are not particularly limited.However, an alkali metal salt, and an alkali earth metal salt arepreferable. Above all, it is preferable that phosphoric acid compound isadded in the form of sodium dihydrogen phosphate, potassium dihydrogenphosphate, disodium hydrogen phosphate, and dibasic potassium phosphate.

The lower limit of the content of phosphoric acid compound is preferably10 ppm or more, and more preferably 30 ppm or more based on phosphateradical. The upper limit is preferably 500 ppm or less, and morepreferably 300 ppm or less. By adding phosphoric acid compound in suchranges, it is possible to obtain EVOH resin composition pellets whichare less colored and not likely to form gel. When the content ofphosphoric acid compound is less than 1 ppm, EVOH is radically coloredat the time of melt molding. In particular, the phenomenon is observedsignificantly when thermal treatment is performed several times. Theproduct obtained by molding the resin composition pellets may be poor inrecycling property. Furthermore, when the content of phosphorouscompound is more that 1000 ppm, gel and hard spots are likely to beformed.

It is preferable that the pellets of EVOH resin composition of the Apresent invention contains a boron compound from the viewpoint ofimproving the thermal stability and mechanical property (JP-49-20675B).When a boron compound is added to an EVOH resin composition, it isthought that a chelate compound is generated between EVOH and the boroncompound. By using such EVOH, it is possible to improve the thermalstability and mechanical property as compared with usual EVOH.

Examples of the boron compound include boric acid, boric acid ester,borate salt, boron hydroxide, and the like. However, the boron compoundis not necessarily limited to these materials. Specifically, examples ofboric acids include orthoboric acid, metaboric acid, tetraboric acid,and the like; examples of boric acids ester include triethyl borate,trimethyl borate, and the like; examples of borate salt include alkalimetal salt, alkali earth metal salt, borax, and the like, of theabove-mentioned various boric acids. Among the above, orthoboric acid(referred to as merely boric acid) is preferable.

The content of boron compound in the pellets of dried resin compositionof EVOH of the present invention is preferably 20-2000 ppm, and morepreferably 50-1000 ppm, based on boron. When the content is less than 10ppm, the effect of improving thermal stability by adding a boroncompound may not be obtained. When the content is more than 2000 ppm,gelling easily occurs, which may lead to formation defects.

By adding alkali metal salts to the pellets of EVOH resin composition ofthe present invention, it is possible to improve the interlayeradhesiveness or compatibility effectively. The additive content ofalkali metal salts in the pellets of dry EVOH resin composition of thepresent invention is 5-5000 ppm, more preferably 20-1000 ppm, andparticularly 30-750 ppm, based on alkali metal atom. An example ofalkali metal includes lithium, sodium, potassium, and the like. Anexample of the alkali metal salt includes aliphatic carboxylate,aromatic carboxylate, phosphate, metal complex of univalent metal, andthe like. A specific example includes sodium acetate, sodium potassium,sodium phosphate, lithium phosphate, sodium stearate, potassiumstearate, sodium of ethylenediaminetetraacetic acid, and the like. Amongthem, sodium acetate, sodium potassium, and sodium phosphate arepreferred.

It is preferable that alkali earth metal salt is added to the pellets ofthe EVOH resin composition of the present invention. When alkali earthmetal salt is added, the effect of improving coloring resistance issomewhat lowered. However, it is possible to further reduce the amountof the thermally deteriorated resin attached to a die of a moldingmachine. There is no particular limitation of alkali earth metal salt.However, magnesium salt, calcium salt, barium salt, beryllium salt, andthe like, generally are used. Magnesium salt and calcium salt areparticularly preferable. There is no particular limitation of anionspecies of alkali earth metal salt, but acetate anion, and phosphateanion are preferred.

The content of the alkali earth metal in the pellets of dry EVOH resincomposition of the present invention is preferably 10-1000 ppm, and morepreferably 20-500 ppm, based on alkali earth metal. When the content ofalkali earth metal is less than 10 ppm, the effect of improving thelong-run property may be insufficient. When the content is more than1000 ppm, resin may be radically colored at the time of the meltingresin.

When the above-mentioned at least one additive selected from carboxylicacid, a boron compound, a phosphoric acid compound, alkali metal salt,and alkali earth metal salt is allowed to be contained in the pellets ofEVOH resin composition, at least one of the above-mentioned additives isadded to EVOH having an ethylene content of 3-70 mol % andsaponification degree of 80 mol % or more in the extruder. By adding atleast one of the above-mentioned additives into the extruder, it ispossible to mix at least one of the above-mentioned additives with EVOHand to knead the mixture with extremely good uniformity. With such anembodiment, it is possible to obtain pellets of EVOH resin compositionin which the motor torque and torque variation in the extruder at thetime of molding is small; extruding stability, coloring resistance andlong-run property are excellent; less gel and hard spots occur; andresin is not attached to the die. Moreover, in the present invention,when adding at least one additive selected from carboxylic acid, a boroncompound, a phosphoric acid compound, alkali metal salt, and alkaliearth metal salt, the feed position of carboxylic acid in the extruderis preferably a position where the EVOH in the extruder is melted interms of sufficiently exhibiting the effect of the present invention. Inparticular, it is preferable that the additive is added into awater-containing and molten state EVOH.

Moreover, it is preferable that the extruder has a kneading portion. Inparticular, it is preferable that is a position where additives areadded is a kneading portion of the extruder for homogeneously blendingthe additives.

Furthermore, for the alkali metal salt and a metal salt other thanalkali earth metal salt, salt of metal belonging to the fourth period ofthe periodic table, for example, manganese, zinc, cobalt, and the like,may be used.

There is no particular limitation of how at least one additive selectedfrom carboxylic acid, a boron compound, a phosphoric acid compound,alkali metal salt, and alkali earth metal salt is added. For example,the materials can be added in a form of dry powder, in a form of pastein which a solvent is impregnated, in a state in which the materials aresuspended in a liquid, as a solution in which the materials aredissolved in a solvent, and the like. However, from the viewpoint ofcontrolling the adding amount, and of attaining a homogeneous diffusionof at least one of the above-mentioned additives in EVOH, the method ofadding at least one of the above-mentioned additives as a solution inwhich the additives are dissolved in the solvent is particularlypreferable. Such a solvent is not particularly limited. However, waterpreferably is used because water has a good solubility with respect toat least one of the above-mentioned additives, a merit in terms of cost,an easiness in handling, safety in operation environment, and the like.

There is no particular limitation in the method for adding at least oneadditive selected from carboxylic acid, a boron compound, a phosphoricacid compound, alkali metal salt, and alkali earth metal salt into theEVOH. However, it is preferable that at least one of the above-mentionedadditives is added into the extruder from at least one or two or moreplace(s).

When at least one additive selected from carboxylic acid, a boroncompound, a phosphoric acid compound, alkali metal salt, and alkaliearth metal salt is added to EVOH in a from of a solution, the lowerlimit of the added amount of the solution is preferably 1 part by weightor more, more preferably 3 parts by weight or more, and particularly 5parts by weight or more, with respect to 100 parts by weight of dryEVOH. Furthermore, the upper limit of added amount of the solution ispreferably 50 parts by weight or less, more preferably 30 parts byweight or less, and particularly 20 parts by weight or less, withrespect to 100 parts by weight of dry EVOH. When the added amount of thesolution is less than 1 part by weight, since the concentration of thesolution is generally increased, the effect of improving the diffusionproperty by the addition of at least one of the above-mentionedadditives may be lowered. Furthermore, when the added amount is morethan 50 parts by weight, it may be difficult to control the watercontent of EVOH, and thus phase separation between resin and watercontained in the resin may occur in the resin composition of EVOH in theextruder.

In a conventional method of immersing EVOH in a solution of acidicmaterial and/or metal salt, it was difficult to produce high qualityproducts from the crumb-like precipitate of EVOH. According to thepresent invention, it is possible to add at least one additive selectedfrom carboxylic acid, a boron compound, a phosphoric acid compound,alkali metal salt, and alkali earth metal salt into EVOH having such ashape, and thus pellets of EVOH resin composition of a stable qualitycan be obtained.

The method of pelletizing the resin composition of EVOH discharged fromthe extruder is not particularly limited. An example includes a methodof extruding the resin composition from dies into a coagulation bath inthe form of a strand, and cutting the strand into an appropriate length.From the viewpoint of handling pellets easily, the aperture diameter ofthe dies is preferably 2-5 mm φ (φ denotes a diameter and the same istrue hereinafter). Preferably, the strand is cut into a length of about1-5 mm.

In general, the resultant pellets are dried. The water content of thepellets of the resin composition of EVOH after drying is generally 1weight % or less, and preferably 0.5 weight % or less. The drying methodis not particularly limited, however, the ventilation drying method orthe fluid-type drying method can be employed preferably. Also bycombining some drying processes, a multi-step drying process can beemployed. Among them, the method in which pellets are first dried by thefluid-type drying method, followed by drying pellets by the ventilationdrying method can be used.

According to one aspect of the present invention, when the cross sectionof the pellets is observed by a polarization microscope (with amagnification of 600), no spherocrystals are observed in the center ofthe cross section. In the pellets produced by the conventional processin which strand is obtained by precipitating EVOH solution aftersaponification and then the strand are cut, spherocrystals are observed(Comparative Example 1). Also, in the pellets obtained by melt moldingEVOH pellets without containing water at high temperature (ComparativeExample 2), spherocrystals are observed. On the other hand, in thepellets of the present invention, no spherocrystals are observed, thusexhibiting a good performance.

According to another aspect of the present invention, although the resinpellet does not contain lubricant, an angle of repose is 23° or lesswhen resin pellets are piled up. With such a low angle of repose, resinscan be fed into the extruder without blocking. It is preferable thatlubricant is not used from the viewpoint of sanitary aspect of the EVOHresin used for food packaging etc. The fact that the lubricant is notused signifies not only that the lubricant is not contained in the resincomposition but also that the lubricant is not attached to the surfaceof the pellets.

In the conventional treating method in which EVOH pellets are immersedin a treating solution containing acid material and/or metal salt, thewater content of EVOH after treatment was generally 40-70 weight %.However, in the method of the present invention in which EVOH is meltedin the extruder and at least one additive selected from carboxylic acid,a boron compound, a phosphoric acid compound, alkali metal salt andalkali earth metal salt is added, it is possible optionally to adjustthe water content of the resin composition of EVOH right after beingdischarged and the water content right after being discharged from theextruder is preferably 5-40 weight %. Therefore, it is possible toobtain pellets having the water content that is lower than that of theconventional pellets. The pellets having such a low water content arepreferable from the viewpoint of reducing the energy consumption in thedrying process.

In particular, the pellets having the water content of more than 40weight % may be melt attached between pellets at the drying temperatureof 100° C. or more. Also, from this viewpoint, the treatment method ofthe present invention is preferable, in which pellets having a low watercontent can be obtained, and at least one additive selected carboxylicacid, a boron compound, a phosphoric acid compound, alkali metal salt,alkali earth metal salt is added.

It is possible to blend EVOH having a different polymerization degree,ethylene content and saponification degree into the EVOH resincomposition pellets obtained by the above-mentioned method, thus meltmolding thereof. Furthermore, it is possible to add the otherreinforcing materials, such as various kinds of plasticizers,stabilizers, surface active agents, colorants, UV ray absorbers,antistatic agents, drying agent, crosslinking agents, metal salts,fillers, various kinds of fibers and the like. The pellet of EVOH resincomposition of the present invention has a small motor torque and torquevariation and excellent extrusion stability. Thus, it is preferable thatthe pellets of the present invention use significantly reduced or nolubricant in some embodiments. However, when a molding is formed of theabove-mentioned pellet, the use of lubricant is an option and notlimited.

Furthermore, it is possible to blend an appropriate amount ofthermoplastic resin other than EVOH in a scope consistent with theobject of the present invention. An example of the thermoplastic resinincludes various kinds of polyolefin (e.g. polyethylene, polypropylene,poly(1-butene), poly(4-methyl)-1-pentene, ethylene-propylene copolymer,copolymer ethylene and α-olefin having 4 or more carbon atoms, copolymerof polyolefin and maleic anhydride, ethylene-vinyl ester copolymer,ethylene-acrylic ester copolymer, or modified polyolefin in which theabove-mentioned olefins are graft-modified with a saturated carboxylicacid or derivatives thereof, and the like), a various kinds of nylon(e.g. nylon-6, nylon-6, 6, nylon-6/6, 6-copolymer, and the like),polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene,polyacrylonitrile, polyurethane, polyacetal and modified polyvinylalcohol resin, and the like.

The resultant pellets of the EVOH resin composition of the presentinvention are melt-molded into various kinds of molded articles, forexample, a film, a sheet, a container, a pipe, a fiber, and the like.Such molded articles are pulverized and molded again for reuse. Thefilm, sheet, fiber etc. can be stretched by a single screw stretchingmethod or a biaxial stretching method. An example of the usable meltmolding method includes extrusion molding, inflation extrusion, blowmolding, melt spinning, injection molding, and the like. The meltingtemperature is preferably 150-270° C., although it differs dependingupon the melting point, etc. of copolymers.

The pellets of the resin composition of EVOH of the present inventionare used practically in a multilayer product that includes at least onelayer of the molded article such as a film, sheet, etc. of thecomposition of the present invention, as well as in a molded articlethat includes a single layer of the present resin composition. Anexample of the laminated structure product includes E/Ad/T, T/Ad/E/Ad/T,and the like, wherein E denotes a an EVOH resin composition of thepresent invention, Ad denotes an adhesive resin, and T denotes athermoplastic resin. However, the present invention is not limited tothis structure alone. The respective layer may be a single layer andoccasionally may be a multilayer.

An example of usful thermoplastic resin includes linear low densitypolyethylene, low density polyethylene, medium density polyethylene,high density polyethylene, an ethylene-vinyl acetate copolymer, anethylene-propylene copolymer, polypropylene, propylene-α-olefincopolymer (α-olefin has 4 to 20 carbon atoms), olefin such aspolybutene, polypentene, etc., or copolymer thereof, polyester such aspolyethylene terephthalate, etc., polyester elastomer, polyamide resinsuch as nylon-6, nylon-6, 6, etc., polystyrene, polyvinyl chloride,polyvinylidene chloride, acrylic resin, vinyl ester resin, polyurethaneelastomer, polycarbonate, chlorinated polyethylene, chlorinatedpolypropylene, and the like. Among them, polypropylene, polyethylene,ethylene-propylene copolymer, ethylene-vinyl acetate copolymer,polyamide, polystyrene, polyester are preferably used.

When laminating EVOH and thermoplastic resin, adhesive resin may beused. In this case, adhesive resin made of carboxylic acid modifiedpolyolefin is preferable. As carboxylic acid modified polyolefin,modified polyolefin copolymer containing carboxylic group, which isobtained by chemically bonding ethylene unsaturated carboxylic acid oranhydride thereof to olefin-based polymer (chemically bonding hereinincludes, bonding by, for example, addition reaction, or graftingreaction). Olefin-based polymer herein denotes polyolefin such aspolyethylene (low pressure, medium pressure, high pressure), linear lowdensity polyethylene, polypropylene, polybutene, and the like, andcopolymer of olefin and a co-monomer (for example, with vinylester,unsaturated carboxylic ester, etc.) capable of copolymerizing olefin.For example, the copolymer is ethylene-vinyl acetate copolymer,copolymer of ethylene and ethyl ester acrylate, and the like. Amongthem, linear low density polyethylene, ethylene-vinyl acetate copolymer(the content of vinyl acetate is 5-55 weight %), and a copolymer ofethylene and ethyl ester acrylate (the content of ethyl ester acrylateis 8-35 weight %) are preferable. Linear low density polyethylene andethylene-vinyl acetate copolymer are particularly preferable. An exampleof ethylene unsaturated carboxylic acid or anhydride thereof includesethylene unsaturated mono-carboxylic acid and ester thereof, ethyleneunsaturated dicarboxylic acid or mono- or di-ester thereof and anhydridethereof. Among them, ethylene unsaturated dicarboxylic acid anhydride ispreferable. A specific example includes maleic acid, fumaric acid,itaconic acid, maleic anhydride, itaconic anhydride, maleic acidmonomethyl ester, maleic acid monoethyl ester, maleic acid diethylester, fumaric acid monomethyl ester, and the like. Particularly, maleicanhydride is preferable.

The amount of ethylene unsaturated carboxylic acid or anhydride thereofto be added or grafted (modification degree) is 0.01 to 15 weight % andpreferably 0.02 to 10 weight % with respect to olefin-based polymer. Theaddition reaction or grafting reaction of ethylene unsaturatedcarboxylic acid to the olefin-based polymer can be obtained by a radicalpolymerization method in the presence of, for example, solvent (xylene,etc.), catalyst (peroxide, etc.) or the like. The melt index (MI) of theresultant carboxylic acid modified polyolefin is preferably 0.2-30 g/10min, and more preferably 0.5-10 g/10 min when measured by D-1238-65T inaccordance with ASTM-D1238 at 190° C. These adhesive resins may be usedsingly or in combination of two layers or more.

In the present invention, the above-mentioned multilayer product can beused in various kinds of shapes. However, in order to improve thephysical property of the multilayer product, stretching is alsopreferable. Thereby, it is possible to obtain a stretched film, astretched sheet, and the like, which is free from rupture, pin-hole,stretching inconsistency, and delamination.

For stretching, any of a uniaxial stretching method and a biaxialstretching method may be employed. From the viewpoint of obtaining goodphysical properties, stretching in the highest possible stretching ratiois preferred. In the present invention, it is possible to obtain astretched film, a stretched sheet, and the like, which is free frompin-hole, crack, stretching inconsistency, and delamination at the timeof stretching.

An example of useful stretching method includes a stretching method ofhigher draw ratio from a deep-drawing formation, a vacuum formation,etc., in addition to a roll stretching method, a tenter stretchingmethod, a tubular stretching method, a stretching blow method, and thelike. As the biaxial stretching, any of a simultaneous biaxialstretching method and a sequential stretching method may be employed.The stretching temperature is selected from 80-170° C., and preferablyfrom 100-160° C.

Thus, the stretching is completed, followed by thermal fixation. Thethermal fixation can be carried out by well-known means. The thermalfixation is carried out at 80-170° C. and preferably 100-160° C. for2-600 seconds with the stretched film tensioned. Furthermore, theresultant stretched film may be subjected to a cooling treatment, aprinting treatment, a dry laminating treatment, a solution coating ormelt coating treatment, a bag-making process, a box process, a tubeprocess, split process, and the like.

The shape of the thus obtained multilayer product is optionallyselected. Examples of the shape include film, sheet, tape, bottle, pipe,filament, profile extruded product, and the like. Furthermore, theresultant multilayer product can be subjected to a thermal treatment, acooling treatment, a rolling treatment, a printing treatment, a drylaminating treatment, a solution coating or a melting coat treatment, abag-making treatment, a deep-drawing treatment, a box treatment, a tubetreatment, a split treatment, and the like. The thus obtained film,sheet, container, or the like, are useful for packaging materials ofvarious kinds of products such as foods, drugs, industrial chemicals,agricultural chemicals, or the like.

When the multilayer products are produced, another base material islaminated on one or both surface(s) of the layer made of molded articlessuch as a film, a sheet, etc, which is obtained from the EVOH resincomposition of the present invention. An example of a laminating methodincludes: a method of melt extruding a thermoplastic resin onto themolded articles (film, sheet, etc.); a method of co-extruding resincomposition and other thermoplastic resin onto the base material ofthermoplastic resin, etc.; a method of co-injecting the thermoplasticresin and EVOH resin composition; furthermore, a method of laminating amolded articles obtained from the EVOH resin composition onto a film ora sheet made of resin composition of other base material with a knownadhesive such as an organic titanium compound, an isocyanate compound, apolyester-based compound, etc.; and the like. Among them, the method ofco-extruding the resin composition and other thermoplastic resin ispreferable. Since the EVOH resin composition of the present invention isexcellent in the interlayer adhesiveness, it is preferable as a resincomposition for co-extrusion and a co-extrusion multilayer product usedthereof.

As the method of co-extruding the composition of the present inventionand thermoplastic resin, any of a multi-manifold combining system T diemethod, a feed-block combining system T die method, and an inflationmethod may be employed.

By secondary processing the thus obtained co-extrusion multilayerproduct, various kinds of molded articles (film, sheet, tube, bottle,etc.) can be obtained. The following is an example of the obtainablemolded articles.

(1) A multilayer co-stretched sheet or film produced by uniaxially orbiaxially stretching or biaxially stretching a multilayer product(sheet, film, or the like), and then thermally treating thereof.

(2) A multilayer roll sheet or film produced by rolling a multilayerproduct (sheet, film, or the like).

(3) A multilayer package such as a tray, cup, etc., produced by athermal molding process such as a vacuum molding, a pressure molding,vacuum pressure molding, and the like, a multilayer product (sheet,film, or the like).

(4) A package such as a bottle, cup, etc., produced by stretch blowmolding from a multilayer product (pipe, etc.).

There is no particular limitation to the secondary processing method. Awell-known secondary processing method other than the methods mentionedabove (for example, blow molding) can be employed.

Since in the thus obtained co-extrusion multilayer products andco-injection multilayer products, less gel and hard spots are formed,and fish eye and streaks occur less at the time of forming films, suchproducts can be used for materials for food packages, for example, adeep drawing container, cup, bottle, and the like.

EXAMPLE

Hereinafter, the present invention will be explained with reference toExamples and Comparative Examples but is not limited to them alone.Hereinafter, “%” and “part” are expressed based on weight unlessotherwise noted. Moreover, water herein denotes ion exchange water.

(1) Measurement of Water Content

A sample of water-containing EVOH (20 g) was placed in a well-driedweighing bottle. The sample was dried with a hot-air dryer at 120° C.for 24 hours. The water content of EVOH was calculated from the changein values of weight of EVOH before and after drying. The calculation wasperformed in accordance with the following equation (1).

Water content (weight %)=(weight before drying−weight afterdried)/weight before drying×100   Equation (1)

(2) Measurement of Number of Spherocrystals

The pellets of EVOH resin composition were cut with “Leichelt Ultra-cutS” manufactured by Leica so as to obtain a slice having a thickness of 1μm. A sealing liquid (refractive index: 1.53) was added to the resultantsample slice, which was observed by a polarization microscope(OPTIPHOT-POL manufactured by NIKON CORP.) with a magnification of 600.The center of the pellet (inner part from 0.1 mm or more from thesurface) was examined for spherocrystals.

(3) Measurement of Angle of Repose

An angle of repose was measured by using a measuring device 30 shown inFIG. 2. The measuring device 30 includes a stainless steel butt 31(size: 470 mm×330 mm×80 mm, buff polishing finish (#400 finish)), ahollow cylindrical sample receiver 32 (polyvinyl chloride pipe), asample receiver holder 33 holding the hollow cylindrical sample receiver32, and a supporting ring 34. The hollow cylindrical sample receiver 32is 42 mm in outer diameter, 35 mm in inner diameter, and 365 mm inheight. First, the butt 31 was set on a horizontal plane and the samplereceiver 32 is positioned at the center of the butt 31. The watercontent of the pellet sample was set to be 0.3 weight % or less. Themeasuring environment was kept at the temperature of 20±2° C., and therelative humidity of 65% RH. The pellet sample was collected with asample container (300 ml), and whole sample is gently added into thesample receiver 32. After the sample is added, the sample receiver islifted up gently until the shape of the samples becomes like a mountain.Next, a diameter of the bottom part of the mountain-shaped sample wasread. In reading, diameters of four directions are read in accordancewith the scales marked on lines radially drawn in eight directions onthe butt 31. At this time, the diameter was determined based on thecircumference of the bottom part of the sample with sample. At thistime, samples independently scattered were disregarded. The height ofthe cone of samples (the length between the top part and the bottom partof the mountain-shaped samples) was measured. The height was determinedby crossing the C-type 1st stainless steel scale over the upper part ofthe butt 31, measuring the length between the side of the surface of thescale and the top of the cone of the sample, and subtracting theabove-measured length from the depth of the butt (80 mm). The thusobtained value was made to be the height of the sample cone. Measurementwas performed five times and the average was taken. The angle of reposewas calculated with the following equation and the calculated value wasexpressed by integer of the first digit in accordance with JIS Z 8401and JIS R 9301.

θ=arctan (2 h/D)

wherein θ denotes an angle of repose (°), h denotes the height of thecone of sample (mm), and D denotes the average value of the diameter offour directions (mm).

(4) Determination of Added Minor Component

Determination was performed in accordance with the following method.“Dry pellets” herein denote pellets obtained as follows. The EVOH resincomposition pellets to which at least one selected from carboxylic acid,a boron compound, a phosphoric acid compound, alkali metal salt, andalkali earth metal salt was added were dried at 100° C. for 15 hourswith a fluid-type hot-air dryer and then dried at 100° C. for 15 hourswith a ventilation hot-air dryer.

(4-a) Determination of Carboxylic Acid Content

A sample of dry pellets (20 g) was placed in 100 ml of ion exchangewater and heated at 95° C. for 6 hours to obtain an extract solution.The content of carboxylic acid was determined by neutralizationtitration of the extract solution with 1/50N NaOH. Phenolphtalein wasused as an indicator.

(4-b) Determination of Alkali Metal and Alkali Earth Metal Ion

A sample dry pellets (10 g) was placed in 50 ml of 0.01N aqueoussolution of hydrochloric acid, and stirred at 95° C. for 6 hours. Thestirred aqueous solution was subjected to a quantitative analysis withion chromatography. For a column, ICS-C25 manufactured by YOKOGAWAELECTRIC CORP. was used. For an eluent, an aqueous solution of 5.0 mMtartaric acid and 1.0 mM 2,6-pyridinedicarboxylic acid was used. Indetermination, a calibration curve made with respect to each metalchloride aqueous solution was used. Thus, the amount of alkali metalsalts and the amount of alkali earth metal salts in the dry pellets wereobtained based on metal by using the resultant amount of ions.

(4-c) Determination of Boron Compound

Na₂CO₃ aqueous solution was added to the sample pellets and subjected toan incineration in a platinum crucible at 600° C. Hydrochloric acid wasadded to dissolve the obtained sample. Then, the content of boroncompound in the obtained sample was determined based on boric acid by anICP emission spectral analysis.

(4-d) Determination of Phosphoric Acid Ion

A sample of dry pellets (10 g) was placed in 50 ml of 0.01N aqueoussolution of hydrochloric acid and stirred at 95° C. for 6 hours. Thestirred aqueous solution was subjected to a quantitative analysis withion chromatography. For a column, ICS-A23 manufactured by YOKOGAWAELECTRIC CORP. was used. For an eluent, an aqueous solution containing2.5 mM sodium carbonate and 1.0 mM sodium carbonate was employed. In thedetermination, a calibration curve made with respect to a solution ofphosphoric acid was used. Thus, the amount of phosphorous compound wasobtained based on phosphoric acid radical from the amount of theresultant ion.

(5) Melt Index (MI)

The melt index was measured in accordance with ASTM-D1238 by using amelt indexer under the conditions where the temperature was 190° C. andload was 2160 grams.

(6) Single-layer Film Formation Test

(6-a) Motor Torque and Torque Variation at the Time of Feeding IntoExtruder

A single-layer film of EVOH resin composition was formed by using anextruder having the following specifications and the motor torque andtorque variation of the EVOH resin composition pellets when they areadded into the extruder.

The following are the specifications of the extruder.

Extruder GT-40-A manufactured by PLASTIC TECHNOLOGY CO., LTD. Typesingle screw extruder (non-vent type) L/D 26 CR 3.5 Diameter 40 mm φScrew Single-start full-flight type Rotation number 40 rpm Drivingmachine DC electric motor SCR-DC218B manufactured by SUMITOMO HEAVYINDUSTRIES, LTD. Motor capacity DC 7.5 W (rated 45A) Heater Four-partsplit type Width of die 300 mm Temperature of resin in die 240° C. Speedof taking out resin 10 m/min

(6-b) Gels and Hard Spots

A single layer film of EVOH was formed by using a sample of dry pellets.One hour after the film formation started, the number of gels and harespots (each of which is about 100 μm or larger, and can be visuallyobserved) was counted, and then the converted into a number with respectto 1.0 m². The resultant films were evaluated as follows in accordancewith the number of hard spots.

A: less than 20

B: 20 to 40

C: 40 to 60

D: 60 or more

(6-c) Coloring Resistance

A single layer film of EVOH was formed by using a sample of dry pellets.One hour after the film formation started, films were rolled onto apaper tube and the coloring degree on the end face of the film wasexamined visually. Then, evaluation was performed as follows.

A: no coloring

B: somewhat yellowing

C: yellowing

D: radically coloring

(6-d) Amount of Resin Attached to the Inside Die

A single layer film of EVOH was formed by using a sample of pellets for8 hours. After the film formation started, the EVOH resin inside theextruder was replaced by LDPE of MI=1. Then, the amount of EVOH resinthermally deteriorated and attached to the inside of die was measured.

(7) Rate of Melt Attachment of Pellets

Five hundred grams of pellets of EVOH resin composition after beingdischarged from the extruder were allowed to pass through a 5-mesh metalscreen gently, and then the weight of the melt attached pellets on themetal screen was measured. The occurrence of melt attachment of pelletswas determined from the resultant weight value by the following equation(Equation 2) and shown in weight %.

Occurrence of melt attachment (%)=weight of melt attached pellets(g)×100/500 (g)   (Equation 2)

(8) Surface Water Content

EVOH pellets (10 kg) were centrifuged with a centrifugal separator. Thecentrifugal separator was an upper part removing type centrifugalseparator H-130M manufactured by Kokusan Enshinki K.K. and has thebelow-mentioned specifications. The surface water content of EVOHpellets was calculated from the change in weight between beforecentrifuging and after centrifuging by the following equation (Equation3).

(Specifications of Centrifugal Separator)

Type: H-130 M

Name: upper-part removing type centrifugal separator

Capacitor: 107L (diameter 914 mm×depth 430 mm)

Material: SUS 304

Rotation number: 1000 rpm (510 G)

<Surface water content>

Surface water content (weight %)=[(weight before centrifuge−weight aftercentrifuge)/weight before centrifuge]×100   (Equation 3)

(9) Raw Material Feeding Continuous Test

The raw material feeding continuous test was carried out using avolumetric feeder of the following specifications shown in FIG. 11. Thecontinuous test was carried out for 8 hours and the time from the timein which the test was started to the time in which extrusion defectoccurred was taken.

<Volumetric Single Screw Feeder>

Specification: SVF-25 manufactured by Nippon Seikosho K.K.

Treating amount: 10 kg/hr (capability: 4-20 kg/hr)

Hopper: 30L

Drive: 0.4 KW

Example 1

EVOH having an ethylene content of 32 mol %, a saponification degree of99.5 mol % and a water content of 35 weight % was fed into thetwin-screw extruder shown in FIG. 1. The temperature of resin at thedischarge portion was set to be 100° C. A treating solution made of anaqueous solution of acetic acid/boric acid/sodium acetate/magnesiumacetate/potassium dihydrogen phosphate was added from the minorcomponent feeding portion located at the tip of the discharge portionside shown in FIG. 1. The feeding amount of EVOH per unit time was 10kg/hr (which includes the weight of water contained), and the addedamount of treating solution per unit time was 0.65 L/hr. The treatingsolution has a composition including 4.3 g/L of acetic acid, 15 g/L ofboric acid, 4.6 g/L of sodium acetate, 3.0 g/L of magnesium acetate, and1.4 g/L of potassium dihydrogen phosphate. The following is thespecifications of the twin-screw extruder (FIG. 1 shows a detailedstructure).

Type Twin-screw extruder L/D 45.5 Diameter 30 mm φ Screw Completemeshing in the same direction Rotation number 300 rpm Motor capacity DC22 KW Heater 13-parts split type Number of dies holes 5 holes (holediameter: 3 mm φ) Temperature of resin in dies 105° C. Speed of takingout resin 5 m/min

The water content of the EVOH resin composition pellets after beingdischarged from the extruder was 20 weight %. When the obtained pelletswere dried at 100° C. for 15 hours with a fluid type dryer and thendried at 100° C. for 15 hours with a ventilation dryer, the watercontent was 0.3 weight %. The dried pellet of resin composition of EVOHhad the content of acetic acid of 300 ppm, the content of boron compoundof 270 ppm based on boric acid, and the content of phosphoric acidcompound of 100 ppm based on phosphate radical. The content of alkalimetal salts was: 40 ppm for potassium based on metal and 130 ppm forsodium based on metal. The content of alkali earth metal salts was 50ppm for magnesium based on metal. Furthermore, MI was 1.5 g/10 min.

When the resultant dry pellets were examined for spherocrystals insidethe pellet, no spherocrystals were observed. Furthermore, the angle ofrepose was 22°.

A single layer film was formed of the dry pellets. The motor torque andtorque variation at the time of extrusion, the occurrence of gel andhard spots, coloring resistance and the amount of pellets attached tothe die, were tested.

The following are the specifications of the twin-screw extruder and Tdie used in the tests.

Extruder GT-40-A manufactured by PLASTIC TECHNOLOGY CO., LTD. TypeSingle-screw extruder (non-vent type) L/D 26 CR 3.5 Diameter 40 mm φScrew Single-start full-flight type, nitrided steel surface Rotationnumber 40 rpm Driving machine DC electric motor SCR-DC218B Manufacturedby SUMITOMO HEAVY INDUSTRIES, LTD Motor capacity DC 7.5 KW (rated 45A)Heater 4-parts split type Width of die 300 mm Temperature of resin indies 240° C. Speed of taking out resin 10 m/min

After a single-layer film was formed under the above-mentionedconditions, the motor torque was 220 kg·cm, and the torque variation was50 kg·cm at the time of extrusion. The test for gel and hard spots andcolor resistance test were evaluated as “A” and the amount of the resinattached to the inside of the die was 2.2 grams.

Examples 2 to 4

EVOH pellets were produced by the same manner as in Example 1 exceptthat an ethylene content, the saponification degree, resin temperatureinside the extruder, the water content of the resin before feeding intothe extruder and the water content right after being discharged werechanged as shown in Table 1 and the feeding amount of EVOH per unittime, the feeding amount and the composition of the solution of at leastone additive selected from carboxylic acid, a boron compound, aphosphoric acid compound, alkali metal salt, and alkali earth metal saltare changed as shown in Table 2. Table 1 shows the conditions ofextrusion, Table 2 shows the composition of the treating solution, Table3 shows the composition of the obtained EVOH pellet and Table 4 showsevaluation results.

Comparative Example 1

A 45% methanol solution of ethylene-vinyl acetate copolymer having anethylene content of 32 weight % was placed in a saponification reactor,a sodium hydroxide/methanol solution (80 g/L) was added thereto so as tobe 0.4 equivalent with respect to a vinyl acetate component in thecopolymer, and methanol was added thereto so that the concentration ofthe copolymer was adjusted to 20%. The temperature was raised to 60° C.and reaction was performed for about 4 hours while blowing nitrogen gasinto the reactor. After 4 hours, the reacted product was neutralizedwith acetic acid to stop the reaction. Furthermore, water was suppliedthereto, and a water and methanol solution of EVOH having an ethylenecontent of 32 weight % and saponification degree of 99.5% was obtained.The EVOH solution was extruded from a metal mold having circular holesinto water, thereby allowing the EVOH solution to precipitate in theform of a strand. The strand was cut into pellets having a diameter ofabout 3 mm and a length of about 5 mm. The obtained pellets weredewatered with a centrifugal separator. Furthermore, the operation inwhich a large amount water was added to the dewatered pellets and againdewatered with a centrifugal separator was repeated.

3.5 kg of the thus obtained EVOH pellets (water content: 55 weight %)were immersed in 6 L aqueous solution containing 0.4 g/L of acetic acid,0.4 g/L of sodium acetate, 0.3 g/L of magnesium acetate, 0.1 g/L ofpotassium dihydrogen phosphate, and 0.7 g/L of boric acid at 25° C. for6 hours. After immersing, liquid was removed from the pellet, and theobtained pellet of resin composition of EVOH (water content: 55 weight%) was dried at 80° C. for 15 hours with a fluid type dryer and thendried at 100° C. for 24 hours by using a ventilation dryer. Thus, drypellets (water content: 0.3 weight %) were obtained.

The dried pellet of resin composition of EVOH had the content of aceticacid of 300 ppm, the content of boron compound of 270 ppm based on boricacid, and the content of phosphoric acid compound of 100 ppm based onphosphoric acid radical. The content of alkali metal salts was: 40 ppmfor potassium based on metal and 130 ppm for sodium based on metal. Thecontent of alkali earth metal salts was 50 ppm for magnesium based onmetal. Furthermore, MI was 1.5 g/10 min. Evaluations for the obtainedpellets were made by the same manner as in Example 1. Table 4 shows theevaluation results.

Comparative Example 2

EVOH resin composition pellets were produced with the dried EVOH resincomposition obtained in Comparative Example 1 by using an extruder ofthe following specifications.

The following are the specifications of the extruder.

Extruder GT-40-A manufactured by PLASTIC TECHNOLOGY CO., LTD. TypeSingle-screw extruder (non-vent type) L/D 26 CR 3.5 Diameter 40 mm φScrew Single-start full-flight type, nitriding steel surface Rotationnumber 40 rpm Driving machine DC electric motor SCR-DC218B Manufacturedby SUMITOMO HEAVY INDUSTRIES LTD. Motor capacity DC 7.5 KW (rated 45A)Heater 4-parts split type Die width 6 holes (hole diameter: 3 mm φ)Temperature of resin in dies 250° C. Speed of taking out resin 2 m/min

The resultant pellets of EVOH resin composition were dried at 100° C.for 24 hours with a ventilation dryer to obtain dry pellets (watercontent: 0.3 weight %). The dried pellets of resin composition of EVOHhad the content of acetic acid of 220 ppm, the content of boron compoundof 270 ppm based on boric acid, and the content of phosphoric acidcompound of 100 ppm based on phosphoric acid radical. The content ofalkali metal salts was: 40 ppm for potassium based on metal and 130 ppmfor sodium based on metal. The content of alkali earth metal salts was50 ppm for magnesium based on metal. Furthermore, MI was 1.5 g/10 min.The pellets were examined in the same manner as in Example 1.

The conditions and results mentioned above are shown in Tables 1 to 4.

TABLE 1 [Conditions of extrusion] Water content Adding Right Feedingamount Before after Saponifi- amount of Temperature feeding dischargedEthylene cation of EVOH treating of resin in into from content degree *1solution extruder extruder extruder (mol %) (%) (kg/hr) (L/hr) (° C.)(wt %) (wt %) Ex. 1 32 99.5 10 0.65 100 35 20 Ex. 2 32 99.5 10 0.5 12050 30 Ex. 3 55 90 10 0.45 100 10 10 Ex. 4 5 99 10 0.7 100 30 20 Co. 2 3299.5 10 — 250 0.3 0.3 *1 weight of EVOH in a water-containing state Ex:Example, Co: Comparative Example (the same is true in the followingTables)

TABLE 2 [Composition of treating solution] Phosphoric Alkali AceticBoric acid Alkali earth acid acid compound metal metal (g/L) (g/L) (g/L)salt (g/L) Salt (g/L) Ex.1 4.3 15 NH₂PO₄ 1.4 NaOAc 4.6 Mg(OAc)₂ 3.0 Ex.27.2 — H₃PO₄ 1.6 NaOAc 17.8 Ca(OAc)₂ 4.0 Ex.3 — — H₃PO₄ 2.1 NaH₂PO₄ 10.4— Ex.4 2.1 — H₃PO₄ 0.3 NaOAc 4.6 Ca(OAc)₂ 4.0 Co.1 0.4 0.7 KH₂PO₄ 0.1NaOAc 0.4 Mg(OAc)₂ 0.3

TABLE 3 [Composition of resin composition pellet] Phosphoric AlkaliAlkali earth Acetic Boric acid metal metal acid acid*¹ Compound*² salt*³Salt*⁴ (ppm) (ppm) (ppm) (ppm) (ppm) Ex.1 300 270 100 K 40 Mg 50 Na 130Ex.2 500 — 150 Na 500 Ca 100 Ex.3 — — 500 Na 100 — Ex.4 150 — 30 Na 130Ca 100 Co.1 300 270 100 K 40 Mg 50 Na 130 Co.2 220 270 100 K 40 Mg 50 Na130 *¹: based on boric acid *²: based on phosphoric acid radical *³:based on metal *⁴: based on metal

TABLE 4 [Evaluation results] Extruding stability Quality of pelletTorque at Number the time of sphero- Angle of feeding Quality of filmcrystals of into Torque Attached Gel and (number/ repose extrudervariation amount hard Coloring mm²) (° ) (kg · cm) (kg · cm) in die (g)spots resistance Ex. 1 Not 22 220 50 2.2 A A observed Ex. 2 Not 21 17020 1.4 A B observed Ex. 3 Not 22 185 25 2.9 B B observed Ex. 4 Not 21180 30 1.3 B B observed Co. 1 Observed 25 >1000 >300 3.1 B B Co. 2Observed 26 >1000 >300 3.5 B C

As is apparent from Tables 1 to 4 (particularly from Table 4), inExamples 1 to 4 of the present invention, spherocrystals were notobserved, and the angle of repose was within the range of 21° to 22°.Therefore, the pellets produced in Examples 1 to 4 can be fed into theextruder smoothly, and extruding stability and quality of formed filmsare excellent. On the other hand, the pellets obtained in ComparativeExamples 1 and 2 cannot be fed into the extruder smoothly and extrudingstability of the pellets was not preferable, because, in ComparativeExample 1, acetic acid etc. is adsorbed due to the immersing method, andin Comparative Example 2, the pellets were produced by extrusion moldingof the resin obtained in the Comparative Example 1, and sospherocrystals were observed and the angle of repose was more than 23°.

As mentioned above, according to Examples 1 to 4, by wet-extruding EVOHby using an extruder, it is possible to produce EVOH resin pellets,which reduce a discharge load to the environment, can be fed into anextruder smoothly without being blocked, and are excellent in extrudingstability and thermal stability (long-run property). Furthermore, sincethe treatment can be performed at relatively low temperature, it ispossible to produce EVOH resin pellets in which the polymer is preventedfrom being deteriorated.

Example 5

EVOH having an ethylene content of 32 mol %, the saponification degreeof 99.5 mol % and the water content of 35 weight % and a sodium contentof 1.5 weight % based on metal was fed into a twin-screw extruder shownin FIG. 3. The twin-screw extruder includes a raw material feedingportion, a washing water supply portion, and a dewatering portion. Thedewatering portion was provided with a wedge wire type dewatering slit.0.5 g/L of acetic acid aqueous solution was added from the washing watersupply portion. The feeding amount of EVOH per unit time was 50 kg/hr(which includes the weight of water contained), and the added amount ofaqueous solution of acetic acid per unit time was 600 L/hr. Theretention time of EVOH was 5 minutes. Thereafter, EVOH discharged from astrand die installed at the tip of the extruder was cut in the form of astrand with a pelletizer, to thus obtain pellets. The following are thespecifications of the twin-screw extruder.

Type Twin-screw extruder L/D 42 Diameter 47 mm φ Screw Complete meshingin the same direction Rotation number 450 rpm Temperature of cylinder 95° C. Temperature of dies 120° C. Number of dies hole 5 holes

The water content of the EVOH resin composition pellets after beingdischarged from the extruder was 39 weight %. The content of sodium ionsin the resin was 0.0007 weight % based on metal.

Examples 6 to 9

EVOH pellets were produced by the same manner as in Example 5 exceptthat an ethylene content of EVOH, the saponification degree andextruding conditions such as the feeding amount of EVOH, theconcentration and the adding amount of acetic acid in the washing waterwere changed to those shown in Table 5. Table 6 shows evaluation resultsin terms of a washing property.

Comparative Example 3

0.7 kg of water-containing EVOH pellets having an ethylene content of 32mol %, the saponification degree of 99.5 mol %, the water content of 40weight % and the content of sodium ions of 1.5 weight % based on metalwere immersed in 25 L of 0.5 g/L aqueous solution of acetic acid (30°C.), and washed for 5 minutes, which corresponds to the retention timeof the EVOH in the extruder. Thereby, the washed water-containing EVOHpellets (water content: 40 weight %) were obtained. The obtained pelletswere evaluated in the same manner as in Example 5. Table 6 shows theevaluation results.

Comparative Example 4

0.7 kg of water-containing EVOH pellets having an ethylene content of 55mol %, the saponification degree of 90.0 mol %, the water content of 43weight % and the content of sodium ions is 1.0 weight % based on metalwere immersed in 25 L of 0.5 g/L aqueous solution of acetic acid (30°C.) and washed for 5 minutes, which corresponds to the retention time ofthe EVOH in the extruder. Thereby, the washed water-containing EVOHpellets (water content: 43 weight %) were obtained. The obtained pelletswere evaluated in the same manner as in Example 5. Table 6 shows theevaluation results.

Comparative Example 5

0.7 kg of water-containing EVOH pellets having an ethylene content of 10mol %, the saponification degree of 99.0 mol %, the water content of 45weight %, and the content of sodium ions of 2.0 weight % based on metalwere immersed in 25 L of 0.5 g/L aqueous solution of acetic acid (30°C.) and washed for 5 minutes, which corresponds to the retention time ofthe EVOH in the extruder. Thereby, the washed water-containing EVOHpellets (water content: 45 weight %) were obtained. The pellets wereevaluated by the same manner as in Example 5. Table 6 shows theevaluation results.

TABLE 5 Concentration of acetic Adding Saponifi- Feeding acid in amountof Ethylene cation amount of washing washing content degree EVOH liquidwater (mol %) (%) *1(kg/hr) (g/L) (L/Hr) Ex.5 32 99.5 50 0.5 600 Ex.6 3299.5 50 0.5 300 Ex.7 32 99.5 50 0 600 Ex.8 55 90 50 0.5 600 Ex.9 10 9950 0.5 600 *1: weight of EVOH in a water-containing state

TABLE 6 Water content (wt %)^(*2) Before Right after Content of alkalimetal ion (wt %) extruding extruded from Before into extruder extruderwashing After washed Ex.5 40 39 1.5 0.0007 Ex.6 40 37 1.5 0.0033 Ex.7 4039 1.5 0.0132 Ex.8 43 43 1.0 0.0009 Ex.9 45 46 2.0 0.0041 Co.3 40 40 1.51.3 Co.4 43 43 1.0 0.8 Co.5 45 45 2.0 1.7 (remark) *²: in ComparativeExamples 3 to 5, the water content is a value before and after washing.

In the resin composition pellets of EVOH obtained in Examples 5 to 9 ofthe present invention, sodium ions were washed and removed. The sodiumions may damage the long-run property and appearance, that is,inappropriate content of sodium ions may induce thermal deterioration,thermal decomposition and radical coloring at the time of melt molding.On the other hand, in Comparative Examples 3 to 5, in which EVOH pelletswere immersed in the washing water and washed for the same time as inExamples 5 to 9, sodium ions were neither washed nor removedsufficiently.

Example 10

EVOH having an ethylene content of 32 mol %, the saponification degreeof 99.5 mol %, the content of sodium ions of 1.5 weight % based on metaland the water content of 52 weight % was fed into a twin-screw extrudershown in FIG. 4 at the rate of 10 kg/hr (which includes the weight ofwater contained). The twin-screw extruder includes a raw materialfeeding portion, a washing water supply portion, a dewatering portion,and a minor component adding portion. The dewatering portion wasprovided with a wedge wire type dewatering slit. A circular strand diehaving a diameter of 3 mm and 5 holes was installed at the tip of theextruder. A 0.5 g/L aqueous solution of acetic acid was supplied fromthe washing water supply portion at the rate of 120 L/hr. An aqueoussolution (shown in Table 8) of acetic acid/boric acid/sodiumacetate/magnesium acetate/potassium dihydrogen phosphate was added fromthe minor component adding portion at the rate of 0.65 L/hr. Thetemperature of resin in the strand die was 105° C. The resin compositionof EVOH right after being discharged from the strand die was cooled downin a water bath to be solidified. The solidified strand was cut with apelletizer into columnar pellets having a diameter of 3 mm and thelength of 4 mm. The water content of these pellets was 20 weight %.Table 7 shows the conditions of extrusion, and Table 8 shows the addingamount per unit time and composition of the adding solution. Thefollowing are the specifications of the twin-screw extruder.

Type Twin-screw extruder L/D 45.5 Diameter 30 mm φ Screw Completemeshing in the same direction Dewatering portion Dewatering slitRotation number 300 rpm Motor capacity DC 22 KW Heater 13-parts splittype Number of dies hole 5 holes (hole diamieter:3 mm φ) Speed of takingout resin 5 m/min

The obtained pellets were dried at 110° C. for 12 hours with a hot-airdryer to reduce the water content to 0.3 weight %. MI of the resincomposition pellet of EVOH after drying was 1.5 g/10 min. Table 9 showsa composition of the dry pellets. Furthermore, when the dry pellets wereformed into a film by using a single screw extruder and evaluated, geland hard spots and coloring were evaluated as “A”. Table 10 shows theevaluation results.

Comparative Example 6

Similar to Comparative Example 3, 0.7 kg of water-containing EVOHpellets having an ethylene content of 32 mol %, the saponificationdegree of 99.5 mol %, the water content of 40 weight % and the contentof sodium ions of 1.5 weight % based on metal were immersed in 25 L of0.5 g/L aqueous solution of acetic acid (30° C.) and washed for 5minutes, corresponding to the retention time of the EVOH in theextruder. Thus, washed water-containing EVOH pellets (water content: 40weight %) were obtained.

The EVOH pellets were immersed in 10 L of aqueous solution having acomposition shown in Table 8 at 25° C. for 6 hours, followed bycentrifuging the EVOH pellets. The resultant EVOH resin compositionpellets were dried with a fluid type dryer at 80° C. for 3 hours toobtain the water content of 20 weight %, and then dried with a hot-airdryer at 110° C. for 12 hours to reduce the water content to 0.3 weight%. The dry pellets were subjected to the film formation test. Table 9shows the composition and MI of the resin composition pellet of EVOH,and Table 10 shows the evaluation results.

TABLE 7 Ethylene Saponification Feeding Water content (%) ConcentrationAdding amount content degree amount of Before After of acetic of washing(mol %) (mol %) EVOH *(kg/hr) dewatering dewatering acid (g/L) water(g/L) Ex. 10 32 99.5 10 52 20 0.5 120 Co. 6 32 99.5 — 52 — 0.5 —(remark) *amount of EVOH in a water-containing state

TABLE 8 Adding Composition of adding liquid (g/L) amount of Acetic Boricliquid (L/hr) acid acid NaOAc NaH₂PO₄.2H₂O Ex.10  0.65 3.0 11 3.0 0.85Co.6 10* 0.51 0.75 0.50 0.16 (remark) *: amount of liquid for immersingtreatment

TABLE 9 Composition of dry pellets (ppm) Acetic Boric MI (g/10 min) acidacid Na⁺ PO₄ ³⁻ Ex.10 1.5 316 233 127 70 Co.6 1.5 209 227 116 73

TABLE 10 Evaluation results Gel and hard spots Coloring Ex.10 A A Co.6 CC

According to Examples 5 to 10, it is possible to provide EVOH resincomposition pellets having an excellent color resistance and reducingthe occurrence of gel and hard spots formation and the amount of pelletsattached to the die with the thermal deterioration or melt attachment ofresin significantly suppressed. Furthermore, the present inventionprovides a process allowing at least one additive selected fromcarboxylic acid, a boron compound, a phosphoric acid compound, alkalimetal salt, and alkali earth metal salt to be contained homogeneously inEVOH even in the case where it is difficult to precipitate a strandstably and to allow the additives to be contained in EVOH, because EVOHhaving less ethylene content and/or saponification degree was used, orEVOH was precipitated in the form of a strand at high speed in order toimprove the productivity. Furthermore, in the process of allowing acidsubstances and/or metal salts to be contained in EVOH, it is possible toextremely reduce the discharging amount, thus providing a productionprocess that is not require waste water treating equipment, equipmentfor adding acid materials and/or metal salts again, and equipment forremoving impurities in the treating solution.

As mentioned above, the process for producing EVOH resin of Examples 5to 10 of the present invention feeds the resin into the extruder,supplies the washing water from at least one place of the extruder,washes the resin, and discharges the washing water out of at least oneplace located downstream from the washing water supply portion, therebyremoving the residue of saponification catalyst from water-containingand molten or semi-molten EVOH inside the extruder efficiently.Furthermore, it is possible to wash EVOH in a small space. Furthermore,since EVOH can be washed at a relatively low temperature, deteriorationof the polymer can be prevented.

Example 11

EVOH having an ethylene content of 32 mol %, the saponification degreeof 99.5 mol % and the water content of 52 weight % was added into atwin-screw extruder shown in FIG. 5, and extruded from a circular stranddie having a diameter of 3 mm and 5 holes. The twin-screw extruderincludes a raw material feeding portion and a dewatering portion. Thedewatering portion was provided with a wedge wire type dewatering slit.The temperature of the resin at the discharge portion was set to be 105°C. The EVOH right after being discharged from the strand die was cooleddown in a water bath to be solidified. The solidified strand was cutinto columnar pellets having a diameter of 3 mm and a length of 4 mmwith a pelletizer.

The feeding amount of EVOH per unit time was 10 kg/hr (which includesthe weight of water contained), and the amount of water to be removedper unit time was 4.00 kg/hr. Table 11 shows the conditions ofextrusion, and Table 12 shows the evaluation results. Furthermore, thefollowing are the specifications of the twin-screw extruder.

Type Twin-screw extruder L/D 45.5 Diameter 30 mm φ Screw Completemeshing in the same direction Dewatering portion Dewatering slitRotation number 300 rpm Motor capacity DC22KW Heater 13-part split typeNumber of dies holes 5 hoes (hole diameter:3 mm φ) Speed of taking outresin 5 m/min

The water content of the resin composition pellets of EVOH after beingdischarged from the extruder was 20 weight %. The melt attachment rateof the pellets was 0%.

Examples 12 and 13

EVOH pellets were produced in the same manner as in Example 11 exceptthat an ethylene content, the saponification degree, resin temperature,the water content before adding into the twin-screw extruder and thewater content after being discharged from the extruder were changed asshown in Table 1. Table 11 shows the conditions of extrusion, and Table12 shows evaluation results.

Example 14

EVOH pellets were produced in the same manner as in Example 11 exceptthat the dewatering portion employs an open vent instead of thedewatering slit. The resultant pellets were subjected to the meltattachment test. Table 11 shows the conditions of extrusion, and Table12 shows evaluation results.

Comparative Example 7

EVOH pellets having an ethylene content of 32 mol %, the saponificationdegree of 99.5 mol % and the water content of 52 weight % was dried at80° C. for 3 hours by using a fluid type dryer to obtain the watercontent of 20 weight %. The melt attachment rate of the resultantpellets was measured by the same manner as in Example 11. Table 12 showsthe evaluation results.

Comparative Examples 8 and 9

EVOH pellets were produced in the same manner as in Comparative Example7 except that an ethylene content of EVOH pellet, the saponificationdegree, and the water content were changed as shown in Table 11. Table12 shows evaluation results.

TABLE 11 Water content Before After Feeding Amount feeding dischargedEthylene Saponification amount of water into from content degreeTemperature of EVOH discharged extruder extruder (mol %) (%) of resin (°C.) (kg/hr) (kg/hr) (wt %) (wt %) Ex. 11 32 99.5 105 10 4.00 52 20 Ex.12 55 95.0 105 10 3.33 40 10 Ex. 13 10 99.0 150  8 1.12 20 7 Ex. 14 3299.5 105 10 4.00 52 20 Co. 7 32 99.5 — — — 52 20 Co. 8 55 95.0 — — — 4010 Co. 9 10 99.0 — — — 20 7

TABLE 12 Evaluation results Rate of melt attachment (%) Example 11 0Example 12 0 Example 13 0 Example 14 0 Comparative Example 7 3Comparative Example 8 13 Comparative Example 9 2

Example 15

EVOH having an ethylene content of 32 mol %, the saponification degreeof 99.5 mol % and the water content of 52 weight % was fed into atwin-screw extruder shown in FIG. 6 at the rate of 10 kg/hr (whichincludes the weight of water contained). The twin-screw extruderincludes a raw material feeding portion, a dewatering portion and aminor component adding portion. The dewatering portion was provided witha wedge wire type dewatering slit. A circular strand die having adiameter of 3 mm and 5 holes was installed at the tip of the extruder.An aqueous solution (shown in Table 14) of acetic acid/boric acid/sodiumacetate/magnesium acetate/potassium dihydrogen phosphate was added fromthe minor component adding portion at the rate of 0.65 L/hr. At thistime, water was discharged from the dewatering portion at the rate of4.65 kg/hr. The temperature of resin in the strand die was 105° C. TheEVOH resin composition right after being discharged from the strand diewas cooled down in a water bath to be solidified. The solidified strandwas cut into columnar pellets having a diameter of 3 mm and the lengthof 4 mm with a pelletizer. The water content of the pellets was 20weight %. Table 13 shows the conditions of extrusion, and Table 14 showsthe adding amount per unit time and the composition of the addingsolution. The following are the specifications of the twin-screwextruder.

Type Twin-screw extruder L/D 45.5 Diameter 30 mm φ Screw Completemeshing in the same direction Rotation number 300 rpm Motor capacity DC22 KW Heater 13-part split type Number of dies hole 5 holes (holediameter: 3 mm φ) Speed of taking out resin 5 m/min

The melt attachment rate of the obtained pellets was 0%. The pelletswere dried at 110° C. for 12 hours with a hot-air dryer to reduce thewater content to 0.3 weight %. MI of the resin composition pellet ofEVOH after dried was 1.5 g/10 min. Table 15 shows a composition of thedry pellets. Furthermore, when the dry pellets were formed into a filmby using a single screw extruder and the film was evaluated, gel andhard spots and coloring were evaluated as “A”. Table 16 shows theevaluation results.

Examples 16 and 17

EVOH pellets of the resin composition were produced in the same manneras in Example 15 except that an ethylene content of EVOH, thesaponification degree, die temperature, the feeding amount of EVOH perunit time, the water content before adding into the twin-screw extruderand the water content right after being discharged from the extruderwere changed as shown in Table 13 and the amount placed per unit timeand composition of the additives made of an aqueous solution aceticacid/boric acid/sodium acetate or calcium acetate/sodium dihydrogenphosphate or potassium dihydrogen phosphate were changed as shown inTable 14. The thus obtained pellets were evaluated. Table 13 shows theconditions of extrusion, Table 14 shows the composition of additivesolution, Table 15 shows a composition of pellets of EVOH resincomposition and Table 16 shows evaluation results.

Example 18

EVOH pellets were produced in the same manner as in Example 15 exceptthat the dewatering portion employs a barrel having a vacuum vent-portinstead of the barrel having the dewatering slit. The melt attachmentand film formation were evaluated. Table 13 shows the conditions ofextrusion, Table 14 shows the composition of the additive solution,Table 15 shows the composition of pellets of resin composition of EVOH,and Table 16 shows the evaluation results.

Comparative Example 10

EVOH pellets having an ethylene content of 32 mol %, the saponificationdegree of 99.5 mol % and the water content of 52 weight % were immersedin a 10 L aqueous solution having a composition shown in Table 14 for 6hours, followed by centrifuging thereof. The resultant pellets of resincomposition of EVOH were dried at 80° C. for 3 hours with a fluid typedryer to obtain the water content of 20 weight %. The melt attachmentrate of the dry pellets was measured by the same manner as in Example15. Thereafter, the dry pellets were dried at 110° C. for 12 hours witha hot-air dryer to reduce the water content to 0.3 weight %. Theevaluation of the film formation of the dry pellets was made. Table 15shows the composition of the resin composition pellet of EVOH and MI ofthe pellets, and Table 16 shows the evaluation results.

Comparative Examples 11 and 12

EVOH pellets of the resin composition were produced in the same manneras in Comparative Example 10 except that an ethylene content of EVOH,the saponification degree, and the water content were changed as shownin Table 13, and the composition of the treating solution, for which theEVOH was immersed, made of an aqueous solution acetic acid/boricacid/sodium acetate or calcium acetate/sodium dihydrogen phosphate orpotassium dihydrogen phosphate was changed as shown in Table 14. Theresultant pellets were evaluated. Table 15 shows a composition ofpellets of EVOH resin composition and Table 16 shows evaluation results.

TABLE 13 Water content Amount Before After Saponi- Feeding of waterfeeding discharged Ethylene fication amount of dis- into from contentdegree EVOH charged extruder Extruder (mol %) (%) (kg/hr) (kg/hr) (wt %)(wt %) Ex.15 32 99.5 10 4.65 52 20 Ex.16 55 95.0 10 3.44 40 15 Ex.17 1099.0  8 1.13 20 12 Ex.18 32 99.5 10 4.65 52 20 Co.10 32 99.5 — — 52 20Co.11 55 95.0 — — 40 15 Co.12 10 99.0 — — 20 12

TABLE 14 Amount of adding Composition of additives (g/L) liquid AceticBoric L/hr acid acid NaOAc Ca(OAc)₂.H₂O NaH₂PO₄.2H₂O NH₂PO₄ Ex. 15  0.653.0 11 3.0 — 0.85 — Ex. 16  0.40 0.5 13 — 1.1 0.53 — Ex. 17  0.35 4.0 212.9 — — 1.1 Ex. 18  0.65 3.0 11 3.0 — 0.85 Co. 10 10* 0.51 0.75  0.50 —0.16 — Co. 11 15* 0.07 0.56 —  0.18 0.09 — Co. 12 20* 1.1 0.65  0.77 — — 0.31 (remark) *amount of liquid for immersing treatment

TABLE 15 Composition of additives in dry pellet (ppm) MI Acetic Boric(g/10 min) acid acid Na⁺ Ca²⁺ PO₄ ³⁻ Ex.15 1.5 316 233 127 — 70 Ex.161.8 30 176 7 21 27 Ex.17 1.5 199 206 51 — 48 Ex.18 1.5 301 230 119 — 73Co.10 1.5 209 227 116 — 73 Co.11 1.8 32 170 8 24 29 Co.12 1.5 188 211 52— 50

TABLE 16 Evaluation results Gel and Rate of melt hard spots Coloringattachment (%) Example 15 A A 0 Example 16 A A 0 Example 17 B B 0Example 18 A A 0 Comparative C C 4 Example 10 Comparative C B 13 Example11 Comparative D 8 Example 12

According to Examples 5 to 10, it is possible to provide EVOH resincomposition pellets having an excellent color resistance and reducingthe occurrence of gel and hard spots and the amount of pellets attachedto the die with the thermal deterioration or melt attachment of resinradically suppressed. Furthermore, the present invention provide aprocess of allowing at least one additive selected from carboxylic acid,a boron compound, a phosphoric acid compound, alkali metal salt, andalkali earth metal salt to be contained homogeneously in EVOH even inthe case where it is difficult to precipitate strand stably and to allowthe additives to be contained in EVOH, because EVOH having less ethylenecontent and/or saponification degree was used, or EVOH was precipitatedin the form of a strand at high speed in order to improve theproductivity. Furthermore, in the producing process of allowing acidsubstances and/or metal salts to be contained in EVOH, it is possible toextremely reduce the discharge amount, thus providing a producing methodthat does not require waste water treatment equipment, equipment foradding acid materials and/or metal salts again, and equipment forremoving impurities in the treating solution.

As mentioned above, according to Examples 11 to 18 of the presentinvention, water can be removed effectively by discharging liquid waterand/or vapor water from the water containing EVOH resin in at least oneplace inside the extruder. Furthermore, after the water content of EVOHresin was adjusted, the additives can be added inside the extrudereffectively.

In addition, as compared with the conventional drying method with ahot-air dryer, the deterioration due to heat or coloring at the time ofdrying is small and melt attachment between pellets or between thepellet and the inner wall of the device can be avoided. Furthermore,when it is difficult to allow the strand to precipitate, for example,when EVOH having a low ethylene contents and/or saponification degree isused, or when the high speed strand precipitation was performed in orderto improve the productivity, the present invention can provide a processcapable of uniform drying. Thereby, it is possible to produce theproducts of high quality in a case of using EVOH having a low ethylenecontent and/or the saponification degree, and to improve theproductivity. Example 19

EVOH having an ethylene content of 32 mol %, the saponification degreeof 90.5 mol % and the water content of 40 weight % was supplied into atwin-screw extruder having one dewatering slit shown in FIG. 7, at therate of 42 kg/hr, and the water from EVOH was removed in the form ofliquid water or vapor water to reduce the water content to 23 weight %.Thereafter, EVOH was extruded from the dies having six holes, eachhaving a diameter of 3 mm, installed at the tip of the extruder. Themolten product was cut with a hot cutter (FIGS. 8 and 9) having fourblades at the portion separated a distance of 0.05 mm from the dies. Theresin temperature at this time was 110° C. The flow rate of circulatingwater of the cutter was 30 liter/min.

The discharge linear velocity from the dies at this time was 21 m/min,the rotation number of the blade was 1200 rpm, and the peripheral speedwas 7.5 m/sec.

The shape of the pellets obtained in this process was a sphere pressedand uniaxially crushed (disk shape or flat sphere shape). The diameterthereof seen from the front was 3.3 mm, and the thickness seen from thecross-section was 2.6 mm. The pellet was evaluated by the followingmethods. Table 17 shows the results.

(Specifications of Extruder Used for Evaluation)

Type Twin-screw extruder L/D 42 Diameter 47 mm φ Screw Complete meshingin the same direction Rotation number 450 rpm Cylinder temperature  95°C. Dies temperature 120° C. Number of dies holes 6 holes

(Evaluation of Pellet Size)

The diameters and length of 100 pellets were measured with a caliper.The percentage of the pellets falling in the range of the diameter of3.3±0.2 mm and the thickness of 2.6±0.2 mm was determined. Theevaluation was based on the following.

◯: 90% or more

Δ: 70% or more and less than 90%

×: less than 70%

Example 20

The pellets produced using EVOH having an ethylene content of 20 mol %,the saponification degree of 99.5 mol % and the water content of 40weight % by the same method as in Example 19 were evaluated in terms ofthe accuracy of cutting pellets. Table 17 shows results.

Example 21

The pellets produced using EVOH having an ethylene content of 20 mol %,the saponification degree of 90.0 mol % and the water content of 40weight % by the same method as in Example 19 were evaluated in terms ofthe accuracy of cutting pellets. Table 17 shows results.

Comparative Example 13

Columnar pellets were obtained in the same manner as in Example 19except that the resin was extruded into a cooling bath in the form ofstrand from a strand die and strands were cut with a strand cutterinstead of hot-cutting the molten state resin extruded from theextruder. The strand die is provided with five holes, each having anouter diameter of 3.3 mm, arranged horizontally. The resultant pelletswere evaluated in terms of the cutting accuracy. Table 17 shows theresults.

The diameters and length of 100 pellets, obtained by cutting with astrand cutter, were measured with a caliper. The number of the pelletsfalling within the range of a diameter of 3.3 mm 0.2 mm, and a thicknessof 3.5 mm±0.2 mm was determined. The cutting accuracy was determined inaccordance with the percentage satisfying the above-mentioned range asfollows.

◯: 90% or more

Δ: 70% or more and less than 90%

×: less than 70%

Comparative Example 14

Columnar pellets were produced in the same manner as in Example 20except that the cutting method as in Comparative Example 13 wasemployed. The resultant pellets were evaluated in terms of the cuttingaccuracy. Table 17 shows the results.

Comparative Example 15

Columnar pellets were produced in the same manner as in Example 21except that the cutting method as in Comparative Example 13 wasemployed. The resultant pellets were evaluated in terms of the cuttingaccuracy. Table 17 shows the results.

TABLE 17 Water content (wt %) Cutting Raw After accuracy materialcutting remark Ex.19 ◯ 40 23 No problems Ex.20 ◯ 40 28 No problems Ex.21◯ 40 22 No problems Co.13 Δ 40 22 Strands sometimes cut off Co.14 X 4028 Strands frequently cut off Co.15 X 40 21 Strands frequently cut off

As is apparent from Table 17, since in Examples 19 to 21, EVOH resin wascut by the hot cutting method, the cutting accuracy was good and thecutting property does not suffer from any problems. On the other hand,in Comparative Examples 13 to 15, after polymer was extruded in the formof a strand in the cooling bath, the resin was cut with a strand cutter.There were problems in terms of the cutting accuracy and cuttingproperty.

As mentioned above, in Examples 19 to 21 of the present invention, awater-containing and molten state EVOH resin is extruded from thedischarge portion, and cut in the molten state. Thus, a large amount ofpolymer can be cut effectively in a short time.

Example 22

45% methanol solution of ethylene-vinyl acetate copolymer having anethylene content of 32 weight % was placed in a saponification reactor,a sodium hydroxide/methanol solution (80 g/L) was added thereto so as tobe 0.4 chemical equivalent with respect to a vinyl acetate component inthe copolymer, and methanol was added thereto so as to adjust theconcentration of the copolymer to 20%. The temperature was raised to 60°C. and reaction was performed for about 4 hours while blowing nitrogengas into the reactor. After 4 hours, the reacted product was neutralizedwith acetic acid to stop the reaction. Furthermore, water correspondingto 55 weight % of whole amount of methanol was added so as to obtain asolution of methanol of EVOH, having an ethylene content of 32 weight %,saponification degree of 99.5%, and water. The EVOH solution wasprecipitated in the form of a strand by extruding the solution intowater from a metal mold having a circular opening. The precipitatedproduct was cut into pellets having a diameter of about 3 mm and alength of about 5 mm. The resultant pellets were subjected to repeatedtreatment in which a large amount of water was added and then dewateredtherefrom. 10 kg of dewatered pellets was centrifuged to remove thesurface water. The percentage of the surface water of the thus obtainedpellets was 0 weight %.

EVOH having an ethylene content of 32 mol %, the saponification degreeof 99.5 mol % and the water content of 33 weight % was fed into atwin-screw extruder shown in FIG. 10. The resin temperature at thedischarge portion was 100° C. A treating solution made of an aqueoussolution of acetic acid/boric acid/sodium acetate/magnesiumacetate/potassium dihydrogen phosphate was added from the minorcomponent adding portion (408) as shown in FIG. 10. The feeding amountof EVOH per unit time was 10 kg/hr (which includes water contained). Theadded amount of treatment liquid was 0.67 L/hr. The treating solutionhad a composition including 4.3 g/L of acetic acid, 15 g/L of boricacid, 4.6 g/L of sodium acetate, 3.0 g/L of magnesium acetate, and 1.4g/L of potassium dihydrogen phosphate. The following are thespecifications of the twin-screw extruder. In the raw material feedingcontinuous test, no extruding defect was observed in 8 hours continuousoperation.

<Raw Material Feeding Continuous Test>

Volumetric Single Screw Feeder

Treating Amount: 10 kg/hr (capability: 4 to 20 kg/hr)

hopper: 30L

drive: 0.4 KW

<Extruder>

Type Twin-screw extruder L/D 45.5 Diameter 30 mm φ Screw Completemeshing in the same direction Rotation number 300 rpm Motor capacity DC22 KW Heater 13-part split type Number of dies holes 5 holes (holediameter: 3 mm φ) Temperature of resin in dies 105° C. Speed of takingout resin 5 m/min

The water content of pellets of EVOH resin composition after beingdischarged from the extruder was 20 weight %. After the obtained pelletswere dried at 100° C. for 15 hours with a fluid type dryer and thendried at 100° C. for 15 hours by using a ventilation dryer, the watercontent was 0.3 weight %. Furthermore, MI was 1.5 g/10 min.

A single layer film of EVOH was formed of the resultant dry pellets andexamined for gel and hard spots and coloring.

In the examination of gel and hard spots and a color resistance wasevaluated as “A”.

Furthermore, the resin pellets are not bridged inside the hopper of thefeeder. The raw material resins could be fed stably into the extruder.Furthermore, since the amount of surface water of the pellet is small,the water vapor was not generated at the lower portion of the hopper,raw materials are not melted, and raw material pellets can be fed stablyinto the extruder. Therefore, the added amount of acid and/or metal slatis stable, and the thermal property was not deteriorated. Table 18 showsthe conditions of extrusion, Table 19 shows the composition of treatedliquid, and Table 20 shows evaluation results.

Example 23

EVOH pellets were produced in the same manner as in Example 1 exceptthat an ethylene content, the saponification degree, resin temperature,the water content before adding into the twin-screw extruder and thewater content after being discharged from the extruder were changed asshown in Table 18, and the amount of EVOH to be placed per unit time andthe amount of a solution of at least one selected from the groupconsisting of carboxylic acid, a boron compound, a phosphoric acidcompound, alkali metal salt, and alkali earth metal salt are changed asshown in Table 19. Table 18 shows the conditions of extrusion, Table 19shows the composition of treating solution, and Table 20 showsevaluation results.

Furthermore, the resin pellets were not bridged inside the hopper of thefeeder. The raw material resins could be fed stably into the extruder.Furthermore, since the amount of surface water of the pellet is small,the water vapor was not generated at the lower portion of the hopper,raw materials were not melted, and raw material pellets could be fedstably into the extruder. Therefore, the added amount of acid-metal slatis stable, and the thermal property was not deteriorated.

Comparative Example 16

45% methanol solution of ethylene-vinyl acetate copolymer having anethylene content of 32 weight % was placed in a saponification reactor,a sodium hydroxide/methanol solution (80 g/L) was added thereto so as tobe 0.4 equivalent with respect to a vinyl acetate component of thecopolymer, and methanol was added thereto so as to adjust theconcentration of the copolymer to 20%. The temperature was raised to 60°C. and reaction was performed for about 4 hours while blowing nitrogengas into the reactor. After 4 hours, the reacted product was neutralizedwith acetic acid to stop the reaction. Furthermore, water was suppliedthereto, and a solution of methanol, water and EVOH having an ethylenecontent of 32 weight % and saponification degree of 99.5% was obtained.The EVOH solution was precipitated in the form of a strand by extrudingthe solution into water from a metal mold having circular holes. Theprecipitated product was cut into pellets having a diameter of about 3mm and the length of about 5 mm. The obtained pellets were dewateredwith a centrifugal separator. Furthermore, an operation in which a largeamount water is supplied to the pellets and again dewatered with acentrifugal separator was repeated. The water percentage of the surfacewater of the resultant pellets was 30 weight % and the water content was65 weight %.

When the resultant pellets were subjected to the raw material feedingcontinuous test, 0.5 hours later, they were bridged at the lower part ofthe hopper, and the operation was stopped. Furthermore, when theobtained pellets were formed into films, the appearance was extremelypoor, that is, gel and hard spots were much observed, and coloringoccurred. Table 18 shows the conditions of extrusion, Table 19 shows thetreatment solution and Table 20 shows the evaluation results.

TABLE 18 Water content (%) Feeding Adding amount Temperature Watercontent Before Right after Ethylene Saponification amount of of treatingof resin in of resin feeding into discharged from content degree EVOH *1solution extruder surface extruder extruder (mol %) (%) (kg/hr) (L/hr)(° C.) (%) (wt %) (wt %) Ex. 32 99.5 10.0 0.67 100 0 33 20 22 Ex. 3299.5 11.4 0.67 120 8 41 20 23 Co. 32 98.5 19.1 0.67 120 30 65 20 16 *1:weight of EVOH in a water-containing state

TABLE 19 Acetic Boric Phosphoric Alkali earth acid acid acid compoundAlkali metal metal (g/L) (g/L) (g/L) salt (g/L) salt (g/L) Ex.22 4.3 15KH₂PO₄ 1.4 NaOAc 4.6 Mg(OAc)₂ 3.0 Ex.23 7.2 — KH₂PO₄ 1.6 NaOAc 17.8Ca(OAc)₂ 4.0 Co.16 7.2 — KH₂PO₄ 1.6 NaOAc 17.8 Ca(OAc)₂ 4.0

TABLE 20 Raw material feeding continuous test Quality of formed filmContinuous operation Gel and hard time (hr) spots Coloring Ex.22 >8 A AEx.23 >8 A B Co.16 0.5 C C

As mentioned above, according to Examples 22 and 23, the followingadvantages are attained.

(1) It is possible to prevent the raw materials from being bridged inthe hopper inside the extruder and to feed the raw materials into theextruder.

(2) Since the amount of surface water of the pellet is small, no watervapor is generated at the lower part of the hopper, and thus the rawmaterial is not melt-attached.

(3) Since the raw material pellets are fed into the extruder, the addedamount of acid and/or metal salt is stable. Thereby, the thermalstability is not deteriorated.

As mentioned above, Examples 22 to 23 of the present inventionillustrate a method of melt kneading the water-containing EVOH resin. Byfeeding the pellets into the extruder with the water content of theentire pellets of the resin set to be 0.5 to 70 weight % and the surfacewater content set to be less than 10 weight %, the pellets can be fedinto the extruder effectively.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The embodimentsdisclosed in this application are to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, all changes that come within the meaning and range ofequivalency of the claims are intended to be embraced therein.

What is claimed is:
 1. A process for producing an ethylene-vinyl alcoholcopolymer resin, comprising feeding an ethylene-vinyl alcohol copolymerinto an extruder to form a molten resin, keeping the temperature of themolten resin in the extruder at 70 to 170° C., adding at least oneadditive selected from the group consisting of a carboxylic acid, aboron compound, a phosphoric acid compound, an alkali metal salt, and analkali earth metal salt to the molten resin in the extruder, adjustingan amount of water present in the extruder by supplying or removingwater, and discharging the resin from the extruder, wherein the resinhas a water content right after being discharged of 5 to 40 weight %. 2.The process according to claim 1, comprising adding at least onecarboxylic acid selected from the group consisting of acetic acid andlactic acid.
 3. The process according to claim 1, wherein the additiveis added in the form of an aqueous solution.
 4. The process according toclaim 1, further comprising washing the ethylene-vinyl alcohol copolymerwith washing water, and discharging the washing water in a liquid statefrom at least one place downstream from a washing water supply portionof the extruder, to remove a residue of a saponification catalystpresent in the copolymer.
 5. The process according to claim 4, whereinthe residue of a saponification catalyst is an alkali metal ion and thecontent of the ion is 0.1 to 5 weight % based on the metal.
 6. Theprocess according to claim 4, wherein the washed ethylene-vinyl alcoholcopolymer comprises 0.05 weight % or less of an alkali metal ion basedon metal.
 7. The process according to claim 4, wherein the washing wateris an aqueous solution of an acid having pKa of 3.5 or more at 25° C. 8.The process according to claim 1, wherein adjusting the amount of waterincludes removing liquid water or vapor water, from at least one placeof the extruder.
 9. The process according to claim 8, wherein the wateris removed with at least one selected from the group consisting of adewatering slit and a dewatering hole.
 10. The process according toclaim 1, comprising feeding a pellet of the copolymer into the extruderwhile keeping the entire water bontent of the pellet at the time offeeding into the extruder at 0.5 to 70 weight %, and the surface watercontent of the pellet of the copolymer at less than 10 weight %.
 11. Theprocess according to claim 10, wherein the feeding is a volumetricfeeding comprising feeding the pellet into the extruder with avolumetric feeder.
 12. The process according to claim 1, wherein thetemperature of the molten resin inside the extruder is from 90 to 140°C.
 13. The process according to claim 1, wherein the water content ofthe resin composition right after discharging is from 15 to 30 weight %.14. The process according to claim 1, wherein an ethylene content in theethylene-vinyl alcohol copolymer is from 3 to 70 mol %, and thesaponification degree is from 80 to 100 mol %.
 15. A process forproducing ethylene-vinyl alcohol copolymer resin pellets, comprisingfeeding an ethylene-vinyl alcohol copolymer into an extruder to form amolten resin, keeping the temperature of the resin in the extruder at 70to 170° C., adding at least one additive selected from the groupconsisting of a carboxylic acid, a boron compound, a phosphoric acidcompound, an alkali metal salt, and an alkali earth metal salt to themolten resin in the extruder, adjusting an amount of water by supplyingor removing water in the extruder, discharging the resin from theextruder, wherein the resin has a water content right after beingdischarged of from 5 to 40 weight %, cutting the dischargedethylene-vinyl alcohol copolymer resin, and drying the cut copolymerresin until the water content is 1 weight % or less.
 16. The processaccording to claim 15, wherein the resin is cut in a molten state. 17.The process according to claim 15, wherein cutting is selected from thegroup consisting of a hot-cut method and an under-water cut method. 18.An ethylene-vinyl alcohol copolymer resin pellet, produced by feeding anethylene-vinyl alcohol copolymer into an extruder to form a moltenresin, keeping the temperature of the molten resin in the extruder at 70to 170° C., adding at least one additive selected from the groupconsisting of a carboxylic acid, a boron compound, a phosphoric acidcompound an alkali metal salt, and an alkali earth metal salt to themolten resin in the extruder, adjusting an amount of water present inthe extruder by supplying or removing water, discharging the resin fromthe extruder, wherein the resin has a water content right after beingdischarged of 5 to 40 weight %, and then cutting the dischargedethylene-vinyl alcohol copolymer resin to form resin pellets and dryingthe resin pellets until the water content is 1 weight % or less, whereinno spherocrystals are observed in the center of the cross section of theresin pellet when the cross section is observed with a polarizationmicroscope having a magnification of
 600. 19. An ethylene-vinyl alcoholcopolymer resin pellet, produced by feeding an ethylene-vinyl alcoholcopolymer into an extruder to form a molten resin, keeping thetemperature of the molten resin in the extruder at 70 to 170° C., addingat least one additive selected from the group consisting of a carboxylicacid, a boron compound, a phosphoric acid compound, an alkali metalsalt, and an alkali earth metal salt to the molten resin in theextruder, adjusting an amount of water present in the extruder bysupplying or removing water, discharging the resin from the extruder,wherein the resin has a water content right after being discharged of 5to 40 weight %, and then cutting the discharged ethylene-vinyl alcoholcopolymer resin to form resin pellets and drying the resin pellets untilthe water content is 1 weight % or less, wherein the angle of repose is23° or less when the resin pellets are piled.
 20. The ethylene-vinylalcohol copolymer resin pellet according to claim 18, wherein theadditive is at least one carboxylic acid selected from the groupconsisting of acetic acid and lactic acid.
 21. The ethylene-vinylalcohol copolymer resin pellet according to claim 18, wherein thecontent of an alkali metal ion contained in the resin pellets is 0.05weight % or less based on the metal.
 22. The ethylene-vinyl alcoholcopolymer resin pellet according to claim 18, wherein an ethylenecontent in the ethylene-vinyl alcohol copolymer is in the range of 3 to70 mol %, and the saponification degree is in the range of 80 to 100 mol%.
 23. The ethylene-vinyl alcohol copolymer resin pellet according toclaim 19, wherein the additive is at least one carboxylic acid selectedfrom the group consisting of acetic acid and lactic acid.
 24. Theethylene-vinyl alcohol copolymer resin pellet according to claim 19,wherein the content of an alkali metal ion contained in the resinpellets is 0.05 weight % or less based on the metal.
 25. Theethylene-vinyl alcohol copolymer resin pellet according to claim 19,wherein an ethylene content in the ethylene-vinyl alcohol copolymer isin the range of 3 to 70 mol %, and the saponification degree is in therange of 80 to 100 mol %.